The Air Force/NASA Solar Mass Ejection Imager (SMEI) launched January 6, 2003 is now recording whole sky data on each 100-minute orbit. Precise photometric sky maps of the heliosphere around Earth are expected from these data. The SMEI instrument extends the heritage of the HELIOS spacecraft photometer systems that have recorded CMEs and other heliospheric structures from close to the Sun into the anti-solar hemisphere. SMEI rotates once per orbit and views the sky away from Earth using CCD camera technology. To optimize the information derived from this and similar instruments, a tomographic technique has been developed for analyzing remote sensing observations of the heliosphere as observed in Thomson scattering. The technique provides 3-dimensional reconstructions of heliospheric density. The tomography program has been refined to analyze time-dependent phenomena such as evolving corotating heliospheric structures and more discrete events such as coronal mass ejections (CMEs), and this improved analysis is being applied to the SMEI data.

Over the past years we have developed a tomographic technique for using heliospheric remote sensing observations (i.e. interplanetary scintillation and Thomson scattering data) for the reconstruction of the three-dimensional solar wind density and velocity in the inner heliosphere. We describe the basic algorithm on which our technique is based. To highlight the details of the reconstruction algorithm we specifically emphasize the implementation of corotating tomography using IPS g-level and IPS velocity observations as proxies for the solar wind density and velocity, respectively. We provide some insight into the modifications required to expand the technique into a fully time-dependent tomography, and to use Thomson scattering brightness (instead of g-level) as a proxy for the solar wind density.

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 will become available from the Solar Mass Ejection Imager. In this paper, we introduce magnetic field projections from solar surface magnetogram data using the Stanford Current-Sheet Source Surface model at the source surface of our model and extrapolate the magnetic field out to and beyond Earth. The 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

We demonstrate a software application designed for the display and interactive manipulation of 3D heliospheric volume data, such as solar wind density, velocity and magnetic field. The Volume Explorer software exploits the capabilities of the Volume Pro 1000 (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. The application allows stereo and perspective views, and animations of time-sequences. We show examples of three-dimensional heliospheric volume data derived from tomographic reconstructions based on heliospheric remote sensing observations of the heliospheric density and velocity structure. Currently these reconstructions are based on archival IPS and Thomson scattering data. In the near future we expect to add reconstructions based on the all-sky observations from the recently launched Solar Mass Ejection Imager.

Plasma disturbances originating on the Sun, such as coronal mass ejections (CMEs), are a major factor in determining 'space weather' in the near-Earth environment. Virtually the only current source of routine observations of these disturbances as they propagate through the interplanetary medium are interplanetary scintillation (IPS) data. We review current work on time-dependent tomographic reconstructions of the heliospheric density and velocity based on currently available IPS remote sensing observations. We discuss the importance of the tomographic analysis of IPS data for an effective space weather forecast system, in particular in connection with the future Low Frequency Array (LOFAR) instrumentation.

Tomographic techniques developed at UCSD over the last few years incorporate a kinematic model of the solar wind to determine and forecast the large-scale three-dimensional extents of velocity and density using interplanetary scintillation (IPS) observations or Thomson scattering brightness data. In this paper, we introduce magnetic field calculations from the Stanford Current-Sheet Source Surface (CSSS) model into our kinematic model. The CSSS model is used to extrapolate the photospheric magnetic field to a source surface at 15 solar radii (Rs). The UCSD kinematic model convects magnetic field from 15 Rs out to and beyond Earth. We compare the results with in situ data near Earth. The spatial relationship between the heliospheric current sheet and coronal mass ejections (CMEs) is shown in remote views of the inner heliosphere.

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.

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 x 60 degree 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 degrees 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.

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.