UCSD/CASS // Solar Mass Ejection Imager (SMEI)

2008 AGU Fall Meeting

San Francisco, CA, December 15 - 19, 2008

3D tomographic reconstructions of the inner heliosphere have been used for over a decade to visualise and investigate the structure of the solar wind and its various features such as transients and corotating structures. Interplanetary scintillation (IPS) observations of the solar wind have been carried out for a much longer period of time revealing information on the structure of the solar wind and the features within it. Here we present such 3D reconstructions using IPS observations from the Solar Terrestrial Environment Laboratory (STELab) and the Ootacamund (Ooty) Radio Telescope (ORT) of the Whole Heliospheric Interval (WHI) Carrington Rotation 2068. This is part of the world-wide IPS community’s International Heliosphysical Year (IHY) collaboration. We show the structure of the inner heliosphere during this time and how our global reconstructions compare with deep-space spacecraft measurements such as those taken by Wind, ACE, STEREO, and Ulysses in terms of density and velocity.

The Gegenschein is a faint diffuse component of the zodiacal light centered upon the antisolar point; this has now been viewed by the Solar Mass Ejection Imager (SMEI) for over 5 years. SMEI provides unprecedented near-full-sky photometric maps each 102-minute orbit, using data from 3 unfiltered CCD cameras. Its 0.1% photometric precision enables observation over long periods of time, of heliospheric structures having surface brightness down to several S10's (an S10 is the equivalent brightness of a 10th magnitude star spread over one square degree). When individual bright stars are removed from the maps and an empirical sidereal background subtracted, the residue is dominated by the zodiacal light. The sky coverage and duration of these measurements enables a definitive characterization. We describe the analysis method for these data, characterize the average Gegenschein brightness distribution, present empirical formulae describing its shape, and discuss its variation with time.

We report observations and 3D reconstructions of corotating heliospheric structures observed by the Solar Mass Ejection Imager (SMEI). Observations of the inner heliosphere have been carried out on a routine basis by SMEI since its launch in early 2003, and these have been used to measure and map the outward flow of several-hundred CMEs. Most of these observations use short-term variations of brightness from one SMEI orbit to the next (every 102 minutes) to track outward motion. The disadvantage of these orbit\u2013to-orbit analyses is that they cannot measure features that remain stationary relative to the Sun-Earth line (or those which corotate with the Sun) and change slowly over time periods of several days. At UCSD we provide measurements of heliospheric structures relative to a long-term base and, even in these observations, there is little evidence of long-term stationary-standing density structures that corotate. By employing a kinematic model of the solar wind, we reconstruct three-dimensional (3D) solar wind structures from multiple observing lines of sight through the outward-flowing solar wind. By including interplanetary scintillation (IPS) velocity observations from STELab, Japan or from Ooty, India we can extract both the solar wind density and velocity from these analyses to compare with "ground truth" measurements from multi-point, in-situ solar wind measurements from the STEREO, SOHO, Wind, and ACE spacecraft. We define the heliospheric structures by these 3D velocity analyses, and they show that while the velocities map large regions near the ecliptic that corotate, the dense structures that front and follow these regions are far more tenuous.

The Murchison Widefield Array (MWA) is an 8,000-antenna, 80-300 MHz, imaging radio array under construction in Western Australia that features a large field of view, high sensitivity, and accurate polarization and intensity calibration. An MWA prototype has been deployed in the field and construction of the full array will begin in mid- 2009 after the performance of the prototype is evaluated. Understanding the connection between the upper corona and the inner heliosphere with novel low-frequency radio observations is a primary objective of the MWA Solar, Heliospheric, and Ionospheric (SHI) science consortium. This presentation covers progress by the SHI consortium's theory and modeling effort. We show simulations of how Faraday rotation, interplanetary scintillation, and radio burst measurements can track and constrain the transport of magnetic fields, density, and energetic electrons into the heliosphere.

Whole Heliosphere Interval
Data and Modeling Assessment Workshop
Boulder, CO, August 26 - 29, 2008

We present the current state of the UCSD Solar Mass Ejection Imager (SMEI) and interplanetary scintillation (IPS) database maintained and stored on UCSD/CASS Web servers. The IPS database provides real time access of Solar-Terrestrial Environment Laboratory (STELab), Japan IPS data, and provides a variety of higher-level data products derived from these observations to help in Space Weather Forecasting. The up-to-date UCSD SMEI database includes individual SMEI CCD data frames from each of the three SMEI cameras since launch and first light in February 2003, as well as full-sky maps in a sidereal reference frame that preserve the original resolution and photometric precision. Higher-level products from the low-resolution 3D analysis of this database are also maintained from launch up to the present. The IPS data and the modeling capability demonstrated as real-time data access in these analyses are available at the Community Coordinated Modeling Center (CCMC), as are the IPS data from STELab from the year 2000 up to the present. See: http://ips.ucsd.edu/, http://smei.ucsd.edu

SHINE-GEM 2008 Workshop
Zermatt, Utah, June 23 - 27, 2008

Interplanetary scintillation (IPS) observations provide a view of the solar wind at all heliographic latitudes from coronagraph fields of view to solar elongation angles >90 degrees from the Sun. The Solar Mass Ejection Imager (SMEI) provides white-light brightness coverage with a better spatial resolution than IPS from about 20 degrees elongation to the anti-solar direction at 180 degrees elongation. These observations can be used to study the evolution of the solar wind, corotating structure, and solar transients as they propagate out into interplanetary space. We use a three-dimensional (3D) reconstruction technique that obtains perspective views from solar corotating plasma and outward-flowing solar wind as observed from the Earth. This is achieved by iteratively fitting a kinematic solar wind model to IPS radio and SMEI white-light observations. This 3D modeling technique permits reconstruction of the density and velocity structures of coronal mass ejections (CMEs) and other interplanetary transients at a relatively coarse resolution, as well as the background solar wind. The resolutions are better both spatially and temporally when used with SMEI white-light observations to perform density reconstructions. Here we present 3D reconstructions of events which include the 28-30 May 2003, 13-15 May 2005, and December 2006 CME periods as observed by SOHO|LASCO using both (when data are available) multi-system IPS and SMEI observations.

We present the current state of the UCSD Solar Mass Ejection Imager (SMEI) and interplanetary scintillation (IPS) database maintained and stored on UCSD/CASS Web servers. The IPS database provides real time access of Solar-Terrestrial Environment Laboratory (STELab), Japan IPS data, and provides a variety of higher-level data products derived from these observations to help in Space Weather Forecasting. The up-to-date UCSD SMEI database includes individual SMEI CCD data frames from each of the three SMEI cameras since launch and first light in February 2003, as well as full-sky maps in a sidereal reference frame that preserve the original resolution and photometric precision. Higher-level products from this database are maintained for select intervals from launch up to the present. The IPS data and the modeling capability demonstrated as real-time data access in these analyses are available at the Community Coordinated Modeling Center (CCMC), as are the IPS data from STELab from the year 2000 up to the present. UCSD/CASS websites: http://ips.ucsd.edu/ and http://smei.ucsd.edu/

Space Weather Week 2007
Boulder, Colorado, April 29 - May 2, 2008

The Solar Mass Ejection Imager (SMEI) has been operating nearly continuously since "first light" on the Coriolis spacecraft in early February, 2003. We present the current state of the SMEI database maintained and stored on a UCSD/CASS Web server. The up-to-date UCSD database includes individual SMEI CCD data frames from each of the three SMEI cameras since launch as well as single-orbit full-sky maps in a sidereal reference frame that preserve the original resolution and photometric precision. A Web interface to this latter data set describes the database and allows display of these maps in sun-centered ecliptic coordinates, either directly or as running differences. Further processing of the SMEI data for select periods has allowed the removal of zodiacal cloud brightness, auroral signals, bright stars, and the sidereal background. These data are also available on the Web as time series for select locations on these sky maps and sky maps with a long-term base brightness removed. An interface to these SMEI sky maps allow side-by side comparisons of direct and difference sky maps from this data set with those processed by the UCSD low-resolution 3D reconstruction technique.

Chapman Conference on the Solar Wind Interaction with Mar
San Diego, CA, January 22 - 25, 2008

Remote sensing observations of the solar wind over a large range of elongations (angular distances from the Sun) provide a data base for modeling the solar wind in the inner heliosphere, out to and beyond the orbit of Mars. We use interplanetary scintillation (IPS) data from meter-wavelength radio systems (from STELab, Univ. of Nagoya, Japan), and Thomson scattering brightness data (from the Solar Mass Ejection Imager, SMEI) in tomographic reconstructions of the density and radial outflow velocity of the solar wind, both in corotating structures and in transient features such as coronal mass ejections (CMEs). We describe our 3D reconstruction technique that relies on the changing perspective view of solar wind structures from solar rotation and outward flow as observed from Earth. The technique allows reconstruction of solar wind structure of CMEs at a resolution determined by the angular and temporal resolution of the remote sensing data. We obtain estimates of solar wind parameters at specific heliospheric locations (e.g., Earth, Mercury and deep space spacecraft such as Ulysses, and Stereo A and B) as a time series extracted from the 3D density and velocity solutions. Here we discuss the density and velocity obtained at Mars in comparison with the dynamic pressure at Mars as modeled from magnetometer data taken by the Mars Global Surveyor (Crider et al., J. Geophys. Res. 108(A12), 1461, 2003). We emphase variations in dynamic pressure that are related with CMEs observed in the remote sensing observations.

2007 AGU Fall Meeting
San Francisco, CA, December 10 - 14, 2007

he Solar Mass Ejection Imager (SMEI) has observed several comets and traced their plasma tails as far as 10⁸ km from their nucleus. A time sequence of SMEI orbital sky maps displays considerable tail motion and disruption for several of these comets. Tracking these motions versus time, when combined with ephemeris information about their distance from the Earth allows a determination of solar wind speeds and their variation with the location of the comet. In the case of comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR), which passed within about 0.3 AU of Earth in April and May of 2004, the SMEI observations show that speeds during disruptions are typically 50 to 100 km s^-1 less than speeds before and after. Time durations of the disturbances vary between 3 and 8 hours, and correspond to distances traversed by the comets of ~10⁶ km (0.007 AU). We compare these observations with interplanetary scintillation (IPS) three-dimensional tomographic reconstructions and find no evidence that the comet-tail features are due to large-scale density or velocity structures. We also compare these with near-by spacecraft measurements such as the Advanced Composition Explorer (ACE), and find a similar result. This suggests that the comet-tail disruptions are caused by small-scale changes in the solar wind acting over distances that are short compared with 1 AU.

Interplanetary scintillation (IPS) observations of the inner-heliosphere have been carried out on a routine basis for many years using metre-wavelength radio telescope arrays.  By employing a kinematic model of the solar wind, we reconstruct the three-dimensional (3D) structure of the inner-heliosphere from multiple observing lines of sight.  From these reconstructions we extract solar wind parameters such as velocity and density, and compare these to “ground truth” measurements from multi-point in situ solar wind measurements from ACE, Ulysses, STEREO, and the Wind spacecraft, particularly during the International Heliophysical Year (IHY).  These multi-point comparisons help us improve our 3D reconstruction technique. Because our observations show heliospheric structures globally, this leads to a better understanding of the structure and dynamics of the interplanetary environment around these spacecraft.

Solar Mass Ejection Imager (SMEI) observations of the inner heliosphere have been carried out on a routine basis since shortly after its launch on January 6, 2003. By employing a kinematic model of the solar wind, we reconstruct three-dimensional (3D) solar wind structures from multiple observing lines of sight through the outward-flowing solar wind. This model allows us to extract solar wind densities from the SMEI white-light observations and to compare these to multi-point in situ “ground truth” solar wind measurements from instruments aboard the Ulysses, STEREO, ACE, and Wind spacecraft. This facilitates improvements to our 3D reconstruction technique by comparing these reconstructions at multiple points in the inner-heliosphere. Our observations show heliospheric structures globally, and because of this, our reconstructions provide us with a better understanding of the structure and dynamics of the interplanetary environment around each spacecraft, and how these structures are connected back to the Sun.

Ground-based measurements of interplanetary scintillation (IPS) have been used to study the solar wind for many years, but interpretation of the results has always been rendered more difficult by uncertainty about the electron density distribution along the extended line-of-sight from radio source to antenna.  This has been particularly marked in the case of Earth-directed coronal mass ejections (CMEs).  The launch of the STEREO spacecraft, with its Heliospheric Imager (HI) instruments, provides us with the first detailed view of structures in the Sun-Earth line, revealing the motion of large-scale density structures, and greatly reducing the uncertainties in interpreting IPS observations of the speeds of small-scale irregularities embedded within the larger structures. In this poster we present results from a co-ordinated programme of measurements which brings together STEREO HI and two different IPS experiments. We consider two events, one from 2005 in which we use a combination of long-baseline IPS measurements from EISCAT and MERLIN, tomographically-reconstructed 3D density distributions from STELab IPS observations, and SOHO EIT and LASCO images to track the development of an Earth-directed CME. We discuss the remaining uncertainties in this approach and the ways in which STEREO HI images would have assisted with the analysis.  In the second event we combine STEREO HI observations of structures in the solar wind with IPS measurements of solar wind speed from EISCAT and MERLIN and tomographic reconstructions of 3D structure. We discuss the results and present suggestions for future co-ordinated campaigns.

The 4^th CCMC Community Workshop
Arecibo Observatory, Puerto Rico, November 5-8, 2007

(NOT YET AVAILABLE)

Living With A Star Science Workshop
Boulder, CO, September 10 - 13, 2007

White-light Thomson scattering observations by the Solar Mass Ejection Imager (SMEI) have recorded the inner heliospheric response to corotating structures and CMEs. Some of the CMEs are also observed by LASCO and, most recently, the STEREO spacecraft. Here we detail several events in SMEI observations that have also been observed by the LASCO coronagraphs and STEREO spacecraft. We show how SMEI is able to measure CME events starting from their first observation at as close as 20 deg. from the solar disk until they fade away in the SMEI 180 deg. field of view. Our 3D reconstruction technique provides perspective views as observed from Earth, from outward-flowing solar wind. This is accomplished by iteratively fitting the parameters of a kinematic solar wind density model to the SMEI white-light observations and, where possible, including interplanetary scintillation (IPS) velocity data. Comparisons with LASCO and STEREO images for individual events or portions of them allow a detailed view of changes in their structure shape and mass as they propagate outward.

2007 SPIE Optics & Photonics
San Diego, CA, August 26 - 30, 2007

The Solar Mass Ejection Imager (SMEI) instrument consists of three CCD cameras with individual fields of view of 60°×3° that combined sweep a 160° arc of sky. SMEI sweeps the entire sky in one spacecraft orbit of 102 minutes. Individual 4-s exposures from each orbit are assembled into full-sky maps. The primary objective in the SMEI data reduction is to isolate the Thomson-scattering signal from free electrons in the solar wind across the sky. One of the steps needed to achieve the required photometric precision is the individual fitting and removal of stars brighter than 6th magnitude from the full-sky maps. The point-spread function of the SMEI optics has several unusual properties. It has a full width of about one degree, is asymmetric, and varies in width depending on where in the FOV the image is formed. Moreover, the orientation of the PSF on the sidereal sky rotates over 360° over the course of a year. We describe the procedure used to fit and subtract individual stars from the SMEI full-sky maps. A by-product of this procedure are time series with the orbital time resolution for stars brighter than 6th magnitude. These results are used by Buffington et al. (2007, this meeting) to calibrate the SMEI instrument against the LASCO C3 coronagraph.

Surface-brightness responses of the C3 coronagraph in LASCO and of the Solar Mass Ejection Imager (SMEI) are compared, using measurements of a selection of bright stars that have been observed in both instruments. Seventeen stars are selected to be brighter than 4.5 magnitudes, not be known variables, and not have a neighboring bright star. Comparing observations of these determines a scaling relationship between surface-brightness measurements from one instrument to those from the other. We discuss units of surface brightness for the two instruments, and estimate a residual uncertainty for the present scaling relationship.

White-light Thomson scattering observations from the Solar Mass Ejection Imager (SMEI) have recorded the inner heliospheric response to many CMEs. Some of these are also observed from the LASCO and, most recently, the STEREO spacecraft. Here we detail several CME events in SMEI observations that have also been observed by the LASCO and STEREO spacecrafts. We show how SMEI is able to measure CME events from their first observations as close as 20? from the solar disk until they fade away in the SMEI 180? field of view. We employ a 3D reconstruction technique that provides perspective views as observed from Earth, from outward-flowing solar wind. This is accomplished by iteratively fitting the parameters of a kinematic solar wind density model to the SMEI white-light observations and, where possible, including interplanetary scintillation (IPS) velocity data. This 3D modeling technique enables separating the true heliospheric response in SMEI from background noise, and reconstructing the 3D heliospheric structure as a function of time. These reconstructions allow both separation of CME structure from other nearby heliospheric features and a determination of CME mass. Comparisons with LASCO and STEREO images for individual CMEs or portions of them allow a detailed view of changes to the CME shape and mass as they propagate outward.

The technique of interplanetary scintillation (IPS) can be used to probe the interplanetary space between the Sun and the Earth. We combine the large spatial-scale tomographic techniques previously applied to data from the STELab array in Japan, with the finer-scale capabilities of the longer baselines between the systems of MERLIN in the UK, and EISCAT and the ESR in northern Scandinavia. We present results of detailed solar wind velocity measurements and those of solar wind flow-directions, constrained by the largescale tomography through the use of a kinematic model.

SCOSTEP International CAWSES Symposium
Kyoto, Japan, October 23-27, 2007

Combined interplanetary scintillation (IPS) and Solar Mass Ejection Imager (SMEI) remote-sensing observations provide a view of the solar wind at all heliographic latitudes and solar elongations; from ~180 degrees anti-solar, down to coronagraph fields-of-view. They can be used to study the evolution of the solar wind, solar transients (such as mass ejections), and corotating structures out into interplanetary space, both in scintillation-level and in velocity for IPS, and Thomson-scattered white-light brightness for SMEI. Here, we show comparisons of events reconstructed using differeing IPS systems and SMEI (such as those in early November 2004 observed by STELab, ORT, and SMEI) by using a 3D reconstruction technique that obtains perspective views from solar corotating plasma and outward-flowing solar wind as observed from the Earth by iterative fitting of a kinematic solar wind model to the different data sets. We also make comparisons of the structures seen in the 3D reconstructions with in-situ measurements such as those from ACE and Ulysses dependent upon the location(s) of spacecraft.

The availability of data from the Heliospheric Imager instruments on the STEREO spacecraft provide the first detailed view of the Sun-Earth line. Such observations reveal structure and movement of large-scale features, and are perfectly complemented by ground-based radio scintillation (IPS) measurements of speed and direction of small-scale structure. In this paper we present results from a coordinated programme of measurements bringing together STEREO HI, IPS and ionospheric tomography. We combine STEREO HI observations of structures in solar wind with IPS measurements of solar wind speed from EISCAT and MERLIN, while ionospheric tomography data and modelling are used to study the reponse of the Earth's ionosphere to solar wind variations. We discuss the observations and our methodology, before going on to draw conclusions for the events observed and discuss the lessons learned for future observing campaigns.

We have available a UCSD 3D reconstruction technique that obtains perspective views from solar corotating plasma and outward-flowing solar wind as observed from Earth by iteratively fitting a kinematic solar wind model to either Solar Mass Ejection Imager (SMEI) or interplanetary scintillation (IPS) observations or a combination of these two data sets. This 3D modeling techniques permits reconstruction of the density and velocity of corotating structures and CMEs. In this ongoing study, we compare SMEI and STELab observations (both direct and using the 3D reconstructions) from data obtained this year while the Ulysses spacecraft is near the Sun and the STEREO spacecraft are near Earth, and extrapolate these observations to the Ulysses spacecraft. Our observations provide remote-sensing measurements and global context for heliospheric structures which here-to-fore have been interpolated between and extended from multi-spacecraft observations. We do this as well to determine noise from signal in the data sets, to discover the differences between the SMEI and IPS remote-sensing data sets, and to certify the UCSD 3D reconstruction technique by comparison with solar wind in-situ observations from spacecraft distant from Earth.

SHINE 2007 Workshop
Whistler, Canada, July 30 - August 3, 2007

Thomson-scattering observations of the solar corona out to 3 AU from SMEI are analyzed using 3D tomography to give the distribution of electron density (n) in the heliosphere with a time resolution of 6 hours. Interplanetary scintillation (IPS) observations are a nonlinear function of velocity on scales of roughly 200 km. Using the technique from Jackson and Hick (2005), the IPS observations from STELab are analyzed with 3D tomography to obtain the radial velocity (v) throughout the heliosphere with a time resolution of 12 hours. In orbit at the Earth's L1 point, ACE measures the local plasma properties and magnetic field with which the results from these tomographic reconstructions can be compared. The electron density is inferred from ACE observations assuming charge neutrality. Studying the time periods of CME Earth-crossings for a few select events, we will show our results of the comparison between the Thomson-scattering (n), IPS (v), and ACE (n and v) data. We will also show a spatial comparison between the size of the local magnetic structure of ICMEs observed by ACE (including the flux rope orientation in the case of magnetic clouds) and the regional extent and volume of the enhanced electron density and velocity regions from the tomographic reconstructions. These initial "vital" statistics will allow us to begin investigating the structure of the heliosphere as a CME convects outward in the solar wind.

Solar Mass Ejection Imager (SMEI) brightness measurements are analyzed to determine the 3D volumetric density of the 20 January 2005 CME. We use this system to measure the distribution of structure and provide a 3D mass of the ejecta associated with the large CMEs viewed in SMEI observations. The primary mass of the 20 January 2005 CME moves to the northwest of the Sun following the event observed earlier in LASCO coronagraph observations. There are two other very large coronal responses to the coronal energy input beginning around 6:30 UT near the time of CME onset. One of these is the large and extremely prompt Solar Energetic Particle (SEP) proton event observed at Earth beginning about 6:50 UT. Another response is an outward-propagating fast shock that arrives at Earth 34 hours following the event onset. A response that may be attributed to this shock is observed slightly more than 5 days following this at the Ulysses spacecraft situated 5.3 AU from the Sun, 17 degrees south of the ecliptic, and 27 degrees from the Sun-Earth line to the west. SMEI observes the white-light response of this shock at Earth in the interplanetary medium around the spacecraft, and limits the shock extent in 3D.

Asia Oceania Geosciences Society, 4th Annual Assembly
Bangkok, India, 30 July-4 August, 2007

Interplanetary scintillation (IPS) observations provide a view of the solar wind at all heliographic latitudes from around 1 A.U. down to coronagraph fields of view. It can be used to study the evolution of the solar wind and solar transients out into interplanetary space and also the inner heliospheric response to corotating solar structures and coronal mass ejections (CMEs), both in scintillation level and in velocity. With colleagues at STELab, Nagoya University Japan, we have developed near-real-time access of STELab IPS data for use in space-weather forecasting. We use a three-dimensional reconstruction technique that obtains perspective views from solar corotating plasma and outward-flowing solar wind as observed from the Earth by iteratively fitting a kinematic solar wind model to IPS observations. This 3D modeling technique permits reconstructions of the density and velocity structures of CMEs and other interplanetary transients at a relatively coarse resolution. These reconstructions have a solar-rotation cadence with 10° latitudinal and longitudinal heliographic resolution for the corotational model, and a one-day cadence and 20° latitudinal and longitudinal heliographic resolution for the time-dependent model predicated by the numbers of lines of sight available for the reconstructions. When SMEI Thomson-scattering analyses are used, the numbers of lines of sight increase greatly so that density reconstructions can be far-better resolved. Higher resolutions are possible too, when these analyses are used with Ooty IPS data that are also demonstrated in these analyses.

EISCAT workshop 2007
Northern Scandinavia, August 2007

Two-site measurements of interplanetary scintillation have been used to study solar wind velocities for over 30 years, but recent developments using EISCAT and MERLIN have led to new insights into the large-scale structure of the inner heliosphere. In this presentation we discuss these observations and present highlights from recent results. These include evidence of a distinct change in fast solar wind speed between the polar crown outflow and the flow from the equatorwards extension of a polar coronal hole, observations of super-radial expansion of the fast wind at heliocentric distances of 25-80 solar radii and evidence for flow rotation in stream interaction regions and in the solar wind perturbed by the passage of a iCME. We compare our results with those obtained from tomographic reconstructions based on lower-frequency IPS observations from the STELab telescope network in Japan and show that the combination of the two IPS approaches provides a powerful tool for studying solar wind structure.

We present results from Interplanetary Scintillation (IPS)observations made jointly with the EISCAT system in Scandinavia and the MERLIN system in the UK. These results provide evidence of a small but measureable equatorwards velocity component in the fast solar wind typically of the order of 1° - 2° off radial direction. Possible reasons for this expansion and further investigations are discussed.

210^th AAS Meeting
Honolulu, HI, May 27-31, 2007

Solar Mass Ejection Imager (SMEI) and interplanetary scintillation (IPS) observations provide a view of the solar wind at all solar elongations; from 180 degrees anti-solar to as close to the Sun as coronagraph fields of view. They can be used to study the evolution of the solar wind and solar transients out into interplanetary space. In addition, the inner heliospheric response to corotating solar structures and coronal mass ejections (CMEs) can be measured, both in scintillation level and in velocity when using IPS, and through Thomson Scattering when using SMEI. We use a 3D reconstruction technique that obtains perspective views from solar corotating plasma and outward-flowing solar wind as observed from Earth, by iteratively fitting a kinematic solar wind model to both SMEI and IPS observations. This 3D modeling technique permits reconstructions of the density and velocity structures of CMEs and other interplanetary transients. These reconstructions have a temporal cadence and heliographic latitudinal and longitudinal resolution predicated by the amount of data used for time-dependent reconstructions, and can use data from a variety of IPS instruments distributed around the Earth. We highlight the 3D analyses of these different data sets using a series of CME events observed beginning on the Sun 4-7 November 2004. We also apply this technique to determine solar wind pressure ("cram" pressure) at Mars. Results are compared with ram pressure observations derived from Mars Global Surveyor magnetometer data for the years 1999 through 2004, and include a reconstruction of a "back-side" event as seen by SOHO/LASCO.

Space Weather Week 2007
Boulder, Colorado, April 24 - 27, 2007

Solar Mass Ejections Imager (SMEI) observations are routinely combined with interplanetary scintillation (IPS) observations from Nagoya, Japan, to reconstruct solar wind density and velocity structure in the inner heliosphere. We have developed procedures to utilize these data sets to derive the time-dependent boundary conditions, which are then used to drive our numerical heliospheric code ENLIL. We will present the results achieved from numerical simulations of selected complex and violent heliospheric events. Simulated density and velocity structures are compared with kinematic reconstructions and with in-situ observations.

NAM/MIST/UKSP 2007
Preston, England, UK, April, 2007

We present results from Interplanetary Scintillation (IPS) observations made jointly with the EISCAT system in Scandinavia and the MERLIN system in the UK. Prior results have provided evidence of a small but measureable equatorwards velocity component in the fast solar wind typically of the order of 1° - 2° off radial direction. In this paper we present the first results of applying a weak scattering model to these observations, confirming an equatorwards expansion. Possible reasons for this expansion are discussed.

LWS Geostorm CDAW and Conference,
Living With a Star - Coordinated Data Analysis Workshop
Florida Tech - Melbourne, FL, March 5-9, 2007

Interplanetary scintillation (IPS) observations provide a view of the solar wind at all heliographic latitudes from around 1 A.U. down to coronagraph fields of view. It can be used to study the evolution of the solar wind and solar transients out into interplanetary space and also the inner heliospheric response to corotating solar structures and coronal mass ejections (CMEs), both in scintillation level and in velocity. With colleagues at STELab, Nagoya University Japan, we have developed near-real-time access of STELab IPS data for use in space-weather forecasting. We use a three-dimensional reconstruction technique that obtains perspective views from solar corotating plasma and outward-flowing solar wind as observed from Earth by iteratively fitting a kinematic solar wind model to IPS observations. This 3D modeling technique permits reconstructions of the density and velocity structures of CMEs and other interplanetary transients at a relatively coarse resolution. These reconstructions have a solar-rotation cadence with 10° latitudinal and longitudinal heliographic resolution for the corotational model, and a one-day cadence and 20? latitudinal and longitudinal heliographic resolution for the time-dependent model. This technique is used to determine solar wind pressure ("ram" pressure) at Mars. Results are compared with ram pressure observations derived from Mars Global Surveyor magnetometer data for the years 1999 through 2004 and include a reconstruction of a "back-side" event as seen by SOHO|LASCO.

2006 Fall AGU Meeting
San Francisco, CA, December 11 - 15, 2006

The SMEI visible-light cameras provide a photometric skymap for each 102-minute orbit with the objective to observe transient Coronal Mass Ejections (CMEs). Zodiacal light is a significant contributor to these maps and must be removed in the data-analysis in order to detect and characterize the much fainter CMEs. We have analyzed over three years of the SMEI calibration data that were taken at the highest spatial resolution to derive the yearly averaged global distribution of zodiacal light between solar elongations of 20° and 180°. Residuals on the individual sky maps from this global average provide information on the detailed geometry of the clouds. We present preliminary results of the analysis, including a characterization of the Gegenschein, possible dust bands, and annual variations.

Solar Mass Ejection Imager (SMEI) brightness measurements are analyzed to determine 3D volumetric densities for several CMEs including that of the 20 January 2005 CME. Here we present analyses of these 3D heliospheric volumetric solar wind density analyses. We use this system to measure the distribution of structure and provide a 3D mass of the ejecta associated with the large CMEs viewed in SMEI observations. In the case of the 20 January 2005 CME, the primary mass moves to the northwest of the Sun following the event observed earlier in LASCO coronagraph observations. There are two other very large coronal responses to the coronal energy input beginning around 6:30 UT near the time of CME onset. One of these is the large and extremely prompt Solar Energetic Particle (SEP) proton event observed at Earth beginning about 6:50 UT. Another response is an outward-propagating fast shock that arrives at Earth 34 hours following the event onset. A response that may be attributed to this shock is observed slightly more than 5 days following this at the Ulysses spacecraft situated 5.3 AU from the Sun, 17° south of the ecliptic, and 27° from the Sun-Earth line to the west. SMEI observes the white-light response of this shock at Earth in the interplanetary medium around the spacecraft, and limits the shock extent in 3D.

Comet observations have been used as in situ probes of the heliospheric environment since they were used to confirm the existence of the solar wind. Changes in a comet tail's appearance are attributed to changes in the solar wind flow. Large scale tail disruptions are usually associated with boundary crossings of the current sheet or, more rarely, impacts from coronal mass ejections. The Solar Mass Ejection Imager (SMEI) observed three bright comets during April-May 2004: Bradfield (C/2004 F4), LINEAR (C/2002 T7), and NEAT (C/2001 Q4). We had previously reported several comet tail disconnection events (DEs) for both NEAT and LINEAR. Investigation of the entire period further reveals that these two comets showed continual changes in their plasma tails. These changes are characterized by a "smokestack-like" billowing effect punctuated by the disconnections. Bradfield however was remarkably quiescent during this entire period. We present these extended comet observations and offer an analysis and cause of the similarities and disparities of these data.

Multiple reconstructions of the October 28-29, 2003 CME/ICME using white-light observations, ground-based cosmic-ray and in situ magnetic field flux rope modeling show two possible flux-rope configurations that pass Earth on opposite sides of the central symmetry axis of the disturbance. An analysis of flux rope model geometries initiated over a wide range in parameter space to test the uniqueness of the single spacecraft inversion reveals the fit is degenerate over a range of impact parameters such that two solutions are obtained. In one case (fit A) the disturbance passes Earth to the west of the rope center with the rope axis at a low inclination of 20 deg to the ecliptic, similar to the ground-based flux rope analysis by Kuwabara et al. (2004). In the second case (fit B) the disturbance passes Earth to the east of the flux rope axis, with the rope axis more highly inclined at 42 deg from the ecliptic, consistent with the SMEI white-light analysis of Jackson et al. (2006). The current densities in both solutions indicate a nearly force-free structure. Multipoint studies of ICMEs show the radius of curvature in the plane of the rope is between that of a dipole field line connected to the Sun and that of a circular field line connected to the Sun. Assuming a dipole field geometry for the large-scale axial field curvature of the rope results in a 3-D reconstruction for case B that is consistent with the loop structure and observed speed in the white-light LASCO images and SMEI density reconstruction, but not for case A. Multipoint measurements of large-scale solar wind transients is one of the key objectives of the Stereo mission, allowing more accurate 3-D reconstructions of in situ data for comparison with white-light observations. Until they become available, the large-scale axial field orientation and loop geometry of these rope reconstructions provides another tool to constrain magnetic flux rope fits of ICMEs using single spacecraft measurements.

Our team addresses the NASA Living With a Star (LWS) Focused Science Topic "to determine the solar origins of the plasma and magnetic flux observed in an interplanetary Coronal Mass Ejection (ICME)." In short, this team is examining the CME--ICME connection. Our team was formed as a result of awards from the LWS Targeted Research and Technology competition in the fall of 2004. Our team is investigating the detailed relationship between the plasma and magnetic fields in active regions, the source regions of CMEs, and subsequent in situ measurements in interplanetary magnetic clouds. We plan to study this connection through detailed numerical simulations of CME initiation and propagation, theoretical investigations, and studies of the properties of active regions, CMEs, and magnetic clouds. We will discuss the goals of our team, how it fits into NASA's missions, and our progress so far. Research supported by NASA's Living With a Star Program.

The traditional analysis of the CME brightness relied on the assumption that all lines of sight through the CME were parallel due to the large distance between the observer and the event. However, this assumption is not correct when CME observations at large distances from the Sun are concerned. In a recent paper (Vourlidas and Howard, 2006) we have outlined the proper geometry and presented a few theoretical predictions about the brightness evolution of CME launched at various angles relative to the Sun-observer line. In this talk, we use LASCO and SMEI observations of the same events to test our predictions and see how we can use our theoretical framework to interpret the observed CME structures.

Interplanetary scintillation (IPS) observations provide a view of the solar wind at all heliographic latitudes inside the Earth's orbit down to the SOHO|LASCO C2 field-of-view. It can be used to study the evolution of the solar wind as it expands out into interplanetary space. Presented here are results from extremely long-baseline IPS measurements using the EISCAT system located in northern Scandinavia and the MERLIN system located in the United Kingdom. Extremely long-baseline IPS observations provide increased velocity resolution in the line-of-sight and a better indication of off-radial solar wind outflow. The results presented in this presentation clearly show equator-ward over-expansion of the fast solar wind at heliocentric distances ranging from 24 to 84 solar radii - implying divergence of the large-scale magnetic field at interplanetary distances in the fast solar wind. We also present case studies showing flow rotation during the passage of a magnetic cloud and deviation in the direction of solar wind flow across stream interfaces.

SHINE 2006 Workshop
Midway, UT, July 31-August 4, 2006

The Solar Mass Ejection Imager (SMEI) measures a photometric white-light response of the interplanetary medium from Earth-orbit over most of the sky in near real time. In the first three years of operation the instrument has recorded the inner heliospheric response to several hundred CMEs. We illustrate the main data reduction steps used to convert the SMEI data from the raw CCD images to photometrically accurate maps of the sky brightness. This includes: integration of new data into the SMEI data base; conditioning to remove from the raw CCD images an electronic offset and dark current pattern; assembly of the CCD images in a high-resolution sidereal grid using known spacecraft pointing information. The high-resolution grid is reformatted to a lower-resolution set of sidereal maps of sky brightness. From these we remove bright stars, background stars, and a zodiacal cloud model. Time series at selected sidereal locations are extracted and processed further to remo ve aurorae, brigth stars, unresolved star light (primarily from the galactic plane) and other unwanted signals. Time series (with a long-term base removed) are currently used in 3D tomographic reconstructions of the solar wind density structure in the inner heliosphere. The data processing is distributed over multiple PCs running Linux, and, runs as much as possible automatically using recurring batch jobs ('cronjobs') mostly written in Python. The core data processing routines are written in Fortran, C++ and IDL.

Solar Mass Ejection Imager (SMEI) brightness measurements are analyzed to determine 3D volumetric densities. Although more information is gleaned from heliospheric observations when there is also interplanetary scintillation (IPS) velocity data present, the volumetric density information can be obtained from the SMEI instrument-alone 3D analysis of this data set. Here we present analyses of these 3D heliospheric volumetric solar wind density and velocity data. We use this system to measure the distribution of structure and provide 3D mass of the ejecta associated with the large CME viewed in SMEI observations for which the primary mass moves to the northwest of the Sun following the 20 January 2005 CME event observed earlier in LASCO coronagraph observations.

Space Weather Week
Boulder, CO, April 25-28, 2006

Solar Mass Ejection Imager (SMEI) densities can now be rendered volumetrically from brightness obtained from the SMEI instrument throughout its time period of operation. Although more information is gleaned from heliospheric observations when there is also interplanetary scintillation (IPS) velocity data present, the volumetric density information can be obtained from the SMEI instrument-alone 3D analysis of this data set. Here we present a volume rendering system developed for the real time visualization and manipulation of these 3D heliospheric volumetric solar wind density and velocity data. We use this system to measure the distribution of structure and provide 3D mass of the ejecta associated with the large CME viewed in SMEI observations that moves to the northwest of the Sun following the January 20, 2005 event observed earlier in LASCO coronagraph observations.

The Solar Mass Ejection Imager (SMEI) measures a photometric white-light response of the interplanetary medium from Earth-orbit over most of the sky in near real time. In the first three years of operation the instrument has recorded the inner heliospheric response to several hundred CMEs (including the May 28, 2003 and the October 28, 2003 halo CMEs). We present the principal data reduction steps used to process the SMEI data from the time the raw CCD images become available to their final assembly into photometrically accurate maps of the sky brightness. This includes: integration of new data into the SMEI data base; conditioning to remove from the raw CCD images an electronic offset and dark current pattern; placement of the CCD images onto a high-resolution sidereal grid using known spacecraft pointing information. The high-resolution map is reformatted to a lower-resolution set of sidereal maps of sky brightness. From these we remove bright stars, background stars, and a zodiacal cloud model. Time series at selected sidereal locations are extracted and processed further to remove aurorae, brigth stars, unresolved star light (primarily from the galactic plane) and other unwanted signals. Time series (with a long-term base removed) are currently used in 3D tomographic reconstructions.

2005 Fall AGU Meeting
San Francisco, CA, December 5 - 9, 2005

The Solar Mass Ejection Imager provides measurements of the Thomson scattering brightness with near-full sky coverage from Earth orbit. These observations allow three-dimensional reconstruction of the solar wind density and velocity in the inner heliosphere. We discuss how these observations provide context for in situ solar wind observations from other "Great Observatory" satellites near Earth (ACE), other planets (Mars Orbiter) and deep space spacecraft (Ulysses).

The Interplanetary Scintillation (IPS) process allows observation of the inner heliospheric response to CMEs in scintillation level and velocity. With the help of our colleagues in STELab, Japan, we have developed near real time access of these data for use in space weather forecasting. We use a 3D reconstruction technique that obtains perspective views from outward-flowing solar wind as observed from Earth by iteratively fitting a kinematic solar wind model using the IPS observations. This 3D modeling technique permits us to reconstruct the density and velocity structure of CMEs, and other interplanetary transient structure at low resolution (with a one day cadence, and at a 20 deg. latitudinal and longitudinal heliographic resolution). Here we explore the use of this technique to reproduce the solar wind pressure observed at Mars following the aftermath of halo (Earth-directed) CMEs. These CMEs include one that erupted from the Sun on May 27, 2003 and another on October 28, 2003 both of which produced a large response at Mars. In addition we explore the response at Mars and our reconstruction of "backside" (as seen from Earth) halo CMEs.

The Solar Mass Ejection Imager (SMEI) has observed the inner heliospheric response in white light from over 200 CMEs. One of these, on January 20, 2005, produced one of the largest Solar Energetic Particle events ever recorded. We show SMEI orbital difference images and the 3D solar wind reconstruction of this well-observed CME, and demonstrate how we can track its outward motion from approximately 20 deg. from the Sun until it vanishes in the SMEI field of view in the direction of the Ulysses spacecraft. Our 3D reconstruction technique is used to obtain perspective views from outward-flowing solar wind as observed from Earth by iteratively fitting a kinematic solar wind density model using the SMEI white light observations. This 3D modeling technique permits us to separate the heliospheric response in SMEI from background noise, and to estimate the 3D structure and transient heliospheric components of the CME and its speed and mass. We then determine the total energy of the CME that can be used as input to determine the total energy output of the event. More information about the spatial extent and energetics of this CME event can be determined by measurements in-situ from the Ulysses spacecraft that was beyond 5 AU and about 35° west of Earth. Ulysses first detected an extremely fast CME response at the spacecraft 7 days following the event on the Sun and the transient flow continued for several days. The SMEI 3D reconstruction shows the event as it passes Earth to the west and helps to disentangle the CME structure. This will allow a better understanding of which portions of the CME intersect Ulysses, and the 3D trajectories of several CMEs observed earlier in coronagraph and SMEI data.

2005 Joint Assembly AGU, SEG, NABS and SPD/AAS
New Orleans, LA, May 23 - 27, 2005

White-light Thomson scattering observations from the Solar Mass Ejection Imager (SMEI) have recorded the inner heliospheric response to several hundred CMEs including the May 28, 2003 halo CME, the October 28, 2003 halo CME, and numerous other heliospheric structures. Here we show the extent of several well-observed CMEs in SMEI observations, and show how we are able to track events from their first measurements in SMEI approximately 20° from the solar disk until they vanish from the SMEI 180° field of view. Several portions of large CMEs observed by the LASCO coronagraphs can be tracked into the interplanetary medium associated with the initial CME response and the underlying erupting prominence structure. We use a 3D reconstruction technique that obtains perspective views from outward-flowing solar wind as observed from Earth, iteratively fitting a kinematic solar wind density model using the SMEI white light observations and, when available, the Solar-Terrestrial Environment Laboratory (STELab), Japan interplanetary scintillation (IPS) velocity data. This 3D modeling technique allows us to separate the heliospheric response in SMEI from background noise, and to estimate the 3D structure of the CME and its mass. For instance, the analysis shows and tracks outward the northward portion of the loop structure of the October 28, 2003 CME observed as a halo in LASCO images that passes Earth on October 29. We determine an excess mass for this structure of 6.7 x 10¹⁶ g and a total mass including an ambient background of 8.3 x 10¹⁶ g. The very fast structure compared in a 3D pixel to pixel comparison with the IPS velocity data gives a kinetic energy for the northward portion of this event of 2.0 x 10³⁴ erg as it passes Earth.

Space Weather Week
Boulder, CO, April 5 - April 8, 2005

We present a volume rendering system developed for the real time visualization and manipulation of 3D heliospheric volumetric solar wind density and velocity data obtained from the Solar Mass Ejection Imager (SMEI) and interplanetary scintillation (IPS) velocities over the same time period. Our system exploits the capabilities of the VolumePro 1000 board from TeraRecon, Inc., a low-cost 64-bit PCI board capable of rendering up to a 512-cubed array of volume data in real time at up to 30 frames per second on a standard PC. Many volume-rendering operations have been implemented with this system such as stereo/perspective views, animations of time-sequences, and determination of CME volumes and masses. In these visualizations we highlight two time periods where halo CMEs were observed by SMEI to engulf Earth, on May 30, 2003 and on October 29, 2003. We demonstrate how this system is used to measure the distribution of structure and provide 3D mass for individual CME features, including the ejecta associated with the large prominence viewed moving to the south of Earth following the late October CME. We will also demonstrate how a simple Internet connection can be used to remotely manipulate and share these volumes across the continent and the world to interactively view them.

205th AAS Meeting
San Diego, CA, January 9 - 13, 2005

White-light Thomson scattering observations from the Solar Mass Ejection Imager (SMEI) have recorded the inner heliospheric response to the October 28, 2003 CME. Here we detail the extent of this particular CME event in SMEI observations, and we show how we are able to track the event from its first measurement approximately 20° from the solar disk until it fades away in the SMEI 180° field of view. Several portions of this CME that can be tracked into the interplanetary medium are associated with the initial CME response and the underlying erupting prominence structure. We employ a 3D reconstruction technique that provides perspective views from outward-flowing solar wind as observed from Earth. This is accomplished by iteratively fitting the parameters of a kinematic solar wind density model to the SMEI white light observations and to Solar-Terrestrial Environment Laboratory (STELab), interplanetary scintillation (IPS) velocity data. This 3D modeling technique enables separating the true heliospheric response in SMEI from background noise, and reconstructing the 3D heliospheric structure as a function of time. These reconstructions allow both separation of the 28 October CME from other nearby heliospheric structure and a determination of its mass. The preliminary SMEI white light calibration indicates a total mass of 6 x 10¹⁶ g for the ejecta associated with the prominence eruption. The total mass of this CME including possible associated nearby structures may have been as much as ~2 x 10¹⁷ g of inner heliospheric response spread over much of the Earthward-facing hemisphere.

The Solar Mass Ejection Imager (SMEI) records a photometric white-light response of the interplanetary medium from Earth over most of the sky in near real time. In the first two years of operation the instrument has recorded the inner heliospheric response to several hundred CMEs, including the May 28, 2003 and the October 28, 2003 halo CMEs. In this preliminary work we present the techniques required to process the SMEI data from the time the raw CCD images become available to their final assembly in photometrically accurate maps of the sky brightness relative to a long-term time base. Processing of the SMEI data includes integration of new data into the SMEI data base; a conditioning program that removes from the raw CCD images an electronic offset ("pedestal") and a temperature-dependent dark current pattern; an "indexing" program that places these CCD images onto a high-resolution sidereal grid using known spacecraft pointing information. At this "indexing" stage further conditioning removes the bulk of the the effects of high-energy-particle hits ("cosmic rays"), space debris inside the field of view, and pixels with a sudden state change ("flipper pixels"). Once the high-resolution grid is produced, it is reformatted to a lower-resolution set of sidereal maps of sky brightness. From these sidereal maps we remove bright stars, background stars, and a zodiacal cloud model (their brightnesses are retained as additional data products). The final maps can be represented in any convenient sky coordinate system. Common formats are Sun-centered Hammer-Aitoff or "fisheye" maps. Time series at selected locations on these maps are extracted and processed further to remove aurorae, variable stars and other unwanted signals. These time series (with a long-term base removed) are used in 3D tomographic reconstructions. The data processing is distributed over multiple PCs running Linux, and, runs as much as possible automatically using recurring batch jobs ('cronjobs'). The batch scrips are controlled by Python scripts. The core data processing routines are written in several computer languages: Fortran, C++ and IDL.

The Solar Mass Ejection Imager (SMEI) was designed to record a photometric white-light response of the interplanetary medium from Earth over most of the sky in near real time, using Thomson scattered sunlight. In its first two years the instrument has observed several hundred Coronal Mass Ejections. Quantitative interpretations of these data requires that the Analog Data Units (ADUs) of the instrument's CCD responses be converted to an effective stellar brightness. The present work provides a preliminary report on establishing this relationship. An appropriate unit here is an "S10", the equivalent brightness of a 10th magnitude star spread over one square degree. The relationship between ADUs and S10s is established by using the SMEI response to bright stars having known visual magnitude and spectral type. These latter are converted to a "SMEI magnitude" by integrating the various star's spectra over the nominal SMEI bandpass, which extends between 0.4 and 1.1 microns and peaks at 0.7 microns, to obtain a spectral scaling factor which is set to unity for G-type stars and relates visual magnitudes to SMEI magnitudes. The final overall conversion factor is then determined from the ADU measurements of the individual stars. This work was supported in part by NSF contract ATM0331513 and NASA grant NAG 5-134543.

We present a volume rendering system developed for the real time visualization and manipulation of 3D heliospheric volumetric solar wind density and velocity data obtained from the Solar Mass Ejection Imager (SMEI) and interplanetary scintillation (IPS) velocities over the same time period. Our system exploits the capabilities of the VolumePro 1000 board from TeraRecon, Inc., a low-cost 64-bit PCI board capable of rendering up to a 512-cubed array of volume data in real time at up to 30 frames per second on a standard PC. Many volume-rendering operations have been implemented with this system such as stereo/perspective views, animations of time-sequences, and determination of CME volumes and masses. In these visualizations we highlight two time periods where halo CMEs were observed by SMEI to engulf Earth, on May 30, 2003 and on October 29, 2003. We demonstrate how this system is used to measure the distribution of structure and provide 3D mass for individual CME features, including the ejecta associated with the large prominence viewed moving to the south of Earth following the late October CME.

2004 Fall AGU Meeting
San Francisco, CA, December 13 - 17, 2004

The Solar Mass Ejection Imager (SMEI) experiment is fixed to the Coriolis spacecraft and views the sky above Earth using sunlight-rejecting baffles and CCD camera technology. SMEI was designed to provide precise photometric white light images over most of the sky on each 102-minute Earth orbit. The brightness sky maps of the inner heliosphere indicate a rich variety of electron density structures that are produced by the material that propagates through it and its interaction with ambient structures. We present some of the preliminary results of the analysis of these photometric SMEI observations derived by modeling the white light observations such that most of the contaminant signals: stars, the zodiacal cloud and high-energy particle variations are removed. We will also show some of the 3D reconstructions that allow this contaminant signal removal using both interplanetary scintillation (IPS) and SMEI data.

The Solar Mass Ejection Imager (SMEI) instrument provides white-light photometric maps covering most of the sky each orbit of the Coriolis spacecraft. The SMEI differential photometry specification is 0.1% for each 1 square degree sky bin. A labyrinthine baffle reduces scattered sunlight, but for a portion of the data a background residue must also be subtracted to finally reach this specification. We describe this process, and further discuss how bright stars are used to determine an appropriate conversion from the CCD-camera data units to sky surface brightness. Also, the CCD in the camera viewing closest to the Sun operates significantly warmer than expected, which gives rise to a changing population of "hot pixels". We describe a data-analysis process which significantly alleviates the photometric impact of this.

The Solar Mass Ejection Imager (SMEI) experiment provides white-light photometric maps covering most of the sky each orbit of the Coriolis spacecraft. The SMEI differential photometry specification is 0.1% for each 1 square degree sky bin, and was designed to provide precise photometric white light images over most of the sky on each 102-minute Earth orbit in order to map heliospheric structures. One of the brightest contaminant signals observed in SMEI is zodiacal light brightness that must be modeled and subtracted from the data in order to provide heliospheric sky maps free from large background changes. We have devised a technique to remove zodiacal dust brightness from the SMEI maps, and in order to do so accurately measure the asymmetry of the equatorial dust to the ecliptic plane as well as the Gegenschein brightness throughout the year. We present preliminary analyses of these observations for specific intervals during the one and a half year lifetime of SMEI.

The Solar Mass Ejection Imager (SMEI) experiment is fixed to the Coriolis spacecraft and views the sky above Earth using sunlight-rejecting baffles and CCD camera technology. SMEI was designed to provide precise photometric white light images over most of the sky on each 102-minute Earth orbit. The brightness sky maps of the inner heliosphere indicate a rich variety of electron density structures that are produced by the material that propagates through it and its interaction with ambient structures. We present some of the preliminary results of the analysis of these photometric SMEI observations derived by 3D reconstructions that allow contaminant signal removal using both interplanetary scintillation (IPS) velocities and SMEI data. We use these analyses to compare preliminary SMEI tomographic white-light results with IPS velocity for the same time intervals.

We have investigated the global features of interplanetary (IP) disturbances associated with 27-28 May coronal mass ejection (CME) events using interplanetary scintillation (IPS) measurements of the Solar-Terrestrial Environment Laboratory (STEL). Our IPS data taken between 2003 May 28 22h UT and May 29 7h UT showed a set of complex feature of IP disturbances, and most of them are regarded as IP consequences of two full-halo CMEs which occurred in association with the X1.3/2B flare on May 27 23:07 UT and the X3.3 flare on May 28 00:27 UT. Some components of the IP disturbances were discriminated from the IPS data by making the model fitting analysis iteratively. One of the components was an Earth-directed one, which appears to correspond to the IP shock observed by ACE on May 29 18:30 UT. Other components were obliquely propagating ones, which either preceded or followed the Earth-directed one. The global features deduced here are generally in agreement with heliospheric reconstructions made from Solar Mass Ejection Imager (SMEI) measurements.

204th AAS Meeting
Denver, CO, May 30 - June 3, 2004

To optimize the information from individual radio source observations of the sky covering large elongations, we have developed a Computer-Assisted Tomography (CAT) program. We fit STELab (Nagoya University, Japan) interplanetary scintillation (IPS) observations to a time-dependent, three-dimensional heliospheric model. These observations allow us to create "sky maps" covering 10° to 80° in elongation, in which we can track CMEs observed earlier in LASCO coronagraph images. These events have approximately the same shapes and extents as observed closer to the Sun. Here we map several CMEs in 3-dimensions as they move outward to 1 AU. Masses for each of the events are determined from the reconstruction analysis and are compared with plane of the sky masses obtained from calibrated LASCO coronagraph images.

The Solar Mass Ejection Imager (SMEI) was launched in January 2003 into Earth orbit. SMEI is designed to observe heliospheric structures illuminated by Thomson-scattered sunlight. The design specification for SMEI is 0.1% in differential photometry for bright unresolved objects, to enable star removal from the heliospheric maps. Such a near-Earth imager will also provide photometric time-series measurements of these stars as a by-product of this removal process. For each 101-minute orbit, SMEI will deliver near complete sky maps having an expected (1s) photometric resolution of about the equivalent of an 11th magnitude star in a square degree. We will report on progress in establishing the photometric calibrations for the SMEI cameras, and discuss SMEI's potential for delivering photometric time-series measurements, which data can then be applied to the study of variable stars, eclipsing stellar systems, and to search for extrasolar planets by the occultation method.

Space Weather Week
Boulder, CO, April 13 - April 16, 2004

We present a volume rendering system developed for the visualization, and manipulation of 3D heliospheric volume data, such as solar wind density, velocity and magnetic field. Our system exploits the capabilities of the VolumePro 1000 board from TeraRecon, Inc., a low-cost 64-bit PCI board capable of rendering a 512-cubed array of volume data in real time at up to 30 frames per second on a standard PC. Many operations have been implemented such as stereo/perspective views, animations of time-sequences, and determination of CME volumes and masses. We will show examples of three-dimensional heliospheric volumes from tomographic reconstructions of density and velocity using real-time interplanetary scintillation (IPS) data. In the near future we expect to add reconstructions based on the all-sky observations from the recently launched Solar Mass Ejection Imager and employ our system to interactively analyze and visualize the abundant information embedded in these data.

AGU Fall Meeting 2003
San Francisco, USA, December 8 - December 12, 2003

We have designed, built and launched into near-Earth orbit a Solar Mass Ejection Imager (SMEI) capable of observing sunlight that has Thomson-scattered from heliospheric structures of time-varying density. SMEI is designed to observe heliospheric structures such as coronal mass ejections, corotating structures and shock waves, to elongations greater than 90° from the Sun. The instrument was inspired by the heliospheric imaging capability demonstrated by the zodiacal light photometers of the Helios spacecraft. The instrument makes effective use of in situ solar wind data from spacecraft in the vicinity of the imager by extending observations to the surrounding environment and back to the Sun. A near-Earth imager can provide up to three days warning of the arrival of a mass ejection from the Sun. In combination with other imaging instruments in deep space, or alone by making some simple assumptions about the outward flow of the solar wind, SMEI can provide a tomographic analysis of the heliospheric structures surrounding it.

The Solar Mass Ejection Imager (SMEI) has been designed to detect and forecast the arrival of solar mass ejections and other heliospheric structures which are moving towards the Earth. We describe the instrument, which was launched into a Sun-synchronous polar orbit on 6 January, 2003 on board the US DoD Coriolis spacecrafth. SMEI contains three CCD cameras, sensitive over the optical waveband, each with a field-of-view of 60°×3°. The sensitivity is such that it will detect changes in sky brightness equivalent to a tenth magnitude star in one square degree of sky. Each camera takes an image every 4s and the normal telemetry rate is 128 kbits/s. SMEI has a photometric accuracy of around 0.1%. In addition to solar mass ejections, images of stars and the zodiacal cloud are measured to this photometric accuracy once/ orbit (102 minutes)..

Interplanetary scintillation (IPS) measurements are known as one of remote-sensing techniques which enable us to gain access to global features of the solar wind (e.g. quasi-stationary corotating structures, transient streams associated with CMEs). We have carried out a long-term collaboration on the reconstruction of the heliospheric features from IPS measurements made with the 327 MHz four-station system of the Solar-Terrestrial Environment Laboratory (STEL), Nagoya University. Under the collaboration, we have developed the computer-assisted tomography (CAT) analysis method, which allows us to retrieve the 3D distribution of the solar wind velocity and density from IPS data. We also have been making the real-time reconstruction experiment of heliospheric features using STEL IPS data and the CAT method. Based on these results, we propose here the joint observations of IPS and SMEI. The SMEI is a powerful tool to investigate the global heliospheric features, and its capability is complementary to one of IPS observations; That is, SMEI observations provide a high-resolution image of the solar wind density distribution, while IPS observations provide reliable estimates of the solar wind velocity. Therefore, a combination of IPS and SMEI observations is essential for achieving a precise reconstruction of global heliospheric (velocity and density) features by the CAT analysis.

We present a volume rendering system developed for the visualization and manipulation of 3D heliospheric volume data such as solar wind density, velocity and magnetic field. Our system exploits the capabilities of the VolumePro 1000 board from TeraRecon, Inc., a low-cost 64-bit PCI board capable of rendering a 512-cubed array of volume data in real time at up to 30 frames per second on a standard PC. Many operations have been implemented such as stereo/perspective views, animations of time-sequences, and determination of CME volumes and masses. We will show examples of three-dimensional heliospheric volumes from tomographic reconstructions of density and velocity using real-time interplanetary scintillation (IPS) data. In the near future we expect to add reconstructions based on the all-sky observations from the recently launched Solar Mass Ejection Imager and employ our system to interactively analyze and visualize the abundant information embedded in these data.

The Solar Mass Ejection Imager (SMEI) was launched on 6 January 2003, and shortly thereafter raised to a nearly circular orbit at 840 km. Three SMEI CCD cameras on the zenith-oriented CORIOLIS spacecraft cover most of the sky beyond about 20° from the Sun, each 102-minute orbit. Data from this instrument will ultimately provide precision visible-light photometric sky maps. Once starlight and other constant or slowly varying backgrounds are subtracted, the residue is mostly sunlight that has been Thomson-scattered from heliospheric electrons. These maps will enable 3-dimensional tomographic reconstruction of heliospheric density and velocity. This analysis requires 0.1% photometry and background-light reduction below one S10 (the brightness equivalent of a 10th magnitude star per square degree). Thus 10^-15 of surface-reduction is required relative to the solar disk. The SMEI labyrinthine baffle provides roughly 10^-10 of this reduction; the subsequent optics provides the remainder. We analyze data covering a range of angles between the SMEI optical axis and the Sun, or the Moon, to evaluate the full system's stray-light rejection performance.

The Solar Mass Ejection Imager (SMEI) instrument images most of the sky every 105 minutes. From this unique dataset, the brightnesses of stars down to and below the eight magnitude can be measured to investigate their variability. This paper presents the methods developed to extract the stellar brightnesses, and the accuracies obtained as a function of brightness and crowding. Example lightcurves are given.

Our tomographic techniques developed over the last few years are based on kinematic models of the solar wind. This allows us to determine the large-scale three-dimensional extents of solar wind structures using interplanetary scintillation (IPS) observations and Thomson scattering brightness data in order to forecast their arrival at Earth in real time. We are specifically interested in a technique that can be combined with observations presently available from IPS velocity data and with observations which are now becoming available from the Solar Mass Ejection Imager. We use solar surface magnetogram data, and a source surface provided by the Stanford Current-Sheet Source Surface model, to provide input to the UCSD tomography program. The UCSD tomography program extrapolates the magnetic field out to and beyond Earth The latest results are compared with in situ data. Real time projections of these data are available on our web site at: http://cassfos02.ucsd.edu/solar/forecast/index_v_n.html and http://cassfos02.ucsd.edu/solar/forecast/index_br_bt.html
This work was supported at UCSD through MURI grants F49620-01-1-0360 and F49620-01-1-0335, and NSF grant ATM-0208443.

AAS 201st Meeting
Seattle, WA, January, 2003

Coronal mass ejections (CMEs), including halo CMEs, can be observed in interplanetary scintillation (IPS) data. To optimize the information from radio source observations, we model them using a time-dependent three-dimensional tomography program. We depict this heliospheric model as a series of "sky map" images that cover elongations extending from 10° to 80°. These IPS maps show CMEs observed earlier in the LASCO coronagraph images with approximately the same shapes and extents that were seen closer to the Sun. Here, a series of these CME events, including halo CMEs, are mapped as they move outward to distances as great as 1 AU.

Remote sensing observations of the solar wind in the inner heliosphere fill an observational gap between near-Sun remote sensing and near-Earth in-situ data. We use heliospheric tomography to follow solar disturbances from Sun to Earth as the basis for a real-time space weather system. Over the past few years interplanetary scintillation observations from the Solar-Terrestrial Laboratory at Nagoya University, Japan, provided the main source of data. In the near future Thomson scattering observations from the recently launched Solar Mass Ejection Imager (SMEI) will be added. Here we show some recent developments in the visualization techniques used to process the volume data sets produced by the tomographic analyis: solar wind density, velocity and magnetic field. 3D visualization is based on an image rendering engine written in the IDL programming language. In addition, we use hardware-based volume rendering with the Volume Pro PCI board from TeraRecon. This board renders 4D volume data (three spatial, plus the time dimension) in real-time, allowing interactive manipulation of evolving (time-dependent) data sets. This work was supported through NASA grant NAG5-9423 and Air Force MURI grant F49620-01-0359.

AGU Fall Meeting, San Francisco, CA
December 10 - December 14, 2001

Our time-dependent tomographic technique developed over the last few years provides a kinematic model of the solar wind The model, which has one-day time steps, allows us to determine the large-scale three dimensional extents of solar disturbances and to forecast their arrival at Earth in real-time.

We introduce magnetic field predictions from the Stanford Current-Sheet Source Surface model (Zhao and Hoeksema, 1995) at the source surface of our kinematic model and extrapolate the magnetic field out beyond Earth. We show an animated version of the convected magnetic field, and compare results with in situ data near Earth.

Reference: Zhao, X. and J.T. Hoeksema, "Prediction of the interplanetary magnetic field strength", J. Geophys. Res. 100, 19-33, 1995.

We are developing tomographic techniques for analyzing remote sensing observations of heliospheric density and velocity structure as observed in Thomson scattering (e.g. using the Helios photometer data) for eventual use with Solar Mass Ejection Imager (SMEI) observations.

We have refined the tomography program to enable us to analyze time-dependent phenomena, such as the evolution of corotating heliospheric structures and more discrete events such as coronal mass ejections. Both types of phenomena are discerned in our data, and are reconstructed in three dimensions. We use our tomography technique to study the interaction of these phenomena as they move outward from the Sun for several events that have been studied by multiple spacecraft in-situ observations and other techniques.

This work is supported by NASA grant NAG5-8504 and AFOSR grant F49620-01-1-0054.

We demonstrate some of the techniques we currently use for the visualization of heliospheric volume data. Our 3D volume data usually are derived from tomographic reconstructions of the solar wind density and velocity from remote sensing observations (e.g., Thomson scattering and interplanetary scintillation observations). We show examples of hardware-based volume rendering using the Volume Pro PCI board (from TeraRecon, Inc.). This board updates the display at a rate of up to 30 frames per second using a parallel projection algorithm, allowing the manipulation of volume data in real-time. In addition, the manipulation of 4D volume data (the 4th dimension usually representing time) enables the visualization in real-time of an evolving (time-dependent) data set. We also show examples of perspective projections using IDL. This work was supported through NASA grant NAG5-9423.

As part of a long-term investigation of halo-like coronal mass ejections (CMEs) well observed in white light by the SOHO LASCO coronagraphs, we report on a study comparing our catalog of parameters and solar and solar wind associations of halo CMEs with interplanetary disturbances observed with the interplanetary scintillation (IPS) radio array of STE Lab in Japan. We have cataloged over 100 full halo CMEs observed by LASCO from 1996 through 2000. This period covers the first half of solar cycle 23 from activity minimum to maximum. Although the STE Lab observations are limited during each year, nearly all of these CMEs occurring during STE Lab observations were associated with IPS disturbances within a day or so following the halo CME onset time. We will present a summary of these comparisons, and will discuss how the combined data sets can be used to determine key parameters of the 3D shape, structure and propagation of ICMEs. At STE Lab a program is used to find best-fit parameters automatically by matching model calculations to the observed IPS g-value (proportional to plasma density) data. At UCSD a tomographic program is used to reconstruct 3D views of ICMEs using the IPS data in a reconstruction technique based on solar rotation and outward solar wind motion. This work is also pertinent for observations that will be available from the Solar Mass Ejection Imager (SMEI) experiment to be launched next year and, later, from the NASA STEREO mission.

AGU Spring Meeting, Boston, MA
May 29 - June 2, 2001

The Solar Mass Ejection Imager (SMEI) is a collaborative project between the Air Force, UCSD/CASS, and the University of Birmingham, England. It will fly on the CORIOLIS spacecraft, scheduled for launch in September 2002. The platform provides a zenith-pointing, terminator orbit. SMEI's three CCD cameras, each viewing a 3°×60° swath of sky, will provide a visible-light map of nearly the entire sky each 100-minute orbit. The instrument is designed to deliver 0.1% differential photometry, and 10−15 scattered-light reduction whe viewing further than 20° from the Sun. We present the results of laboratory measurements which certify that these specifications are met by the SMEI flight hardware. We will also present night-sky data taken with the SMEI prototype optics, and progress on normalizing, flat-field correcting, and registering the SMEI data into a standard sky coordinate frame.
This work is supported by AFRL contract F19628-00-C-0029.

We are developing tomographic techniques for analyzing remote sensing observations of the coronal and heliospheric density and velocity structure as observed in Thomson scattering (e.g. by the SOHO/LASCO coronagraph and Helios photometers) and interplanetary scintillation (IPS) observations.

We have refined the program to enable us to analyze time-dependent phenomena, such as the evolution of co-rotating heliospheric structures and rapidly evolving events such as coronal mass ejections, as observed e.g. with the future Solar Mass Ejection Imager (SMEI) experiment. We currently provide the three-dimensional analyses in real-time using IPS observations in order to forecast the arrival of CMEs and we intend to show these analyses at our display.

This work is supported by NASA grant NAG5-9423 and NSF grant ATM-9819947.

We are currently developing a tomographic approach for analyzing remote sensing observations of the coronal and heliospheric density and velocity structure (e.g. Thomson scattering and interplanetary scintillation observations). Parallel to the tomographic techniques we are developing the visualization tools required for displaying and manipulating the three-dimensional tomographic results. We use a common graphics interface language (OpenGL, supported through IDL), standard visual interfaces (pop-up menus, sliders, point-and-click methods) and standard hardware (PCs). The visualization should be capable of simultaneously displaying the tomographic density and velocity model and should allow the user to dynamically view the heliospheric model using any predefined flight path through the three-dimensional cube covered by the model. For real-time volume rendering we use a Mitsubishi Volume Pro PCI board. We present our current progress in this visualization effort. Further details can be found on http://casswww.ucsd.edu/solar/index.html.
This work was supported through NASA grant NAG5-9423.

Solar Encounter: The First Solar Orbiter Workshop
May 14 - 18, 2001, Santa Cruz de Tenerife, Spain

We have developed a prototype instrument for use on a near-Sun, three-axis stabilized, solar-oriented platform such as Solar Orbiter. The imager we envision analyzes remotely-sensed observations of coronal and heliospheric brightness in order to provide context for in-situ plasma measurements. With this sensitive instrument, the analysis of these data will proceed much as it has from our recent use of Thomson-scattering observations from the Helios spacecraft together with a recently developed time-dependent tomographic technique for analyzing these observations.

We show a working model of our heliospheric imager for use on Solar Orbiter, scaled-down from the size required at 1 AU. We also show our most recent tomographic result with Helios photometer data that depicts CMEs as well as corotating structures in the heliosphere and gives correlations of these data with in-situ plasma density measurements at the spacecraft.

This work is supported by NASA grant NAG5-9423.