Three dimensional tomography of heliospheric features using global Thomson scattering data Original Research Article

Images of the heliosphere will become available from the Air Force/NASA Solar Mass Ejection Imager (SMEI), and from the all-sky cameras proposed for the NASA missions STEREO, Solar Probe and Solar Polar Sail. To optimize the information available from these instruments, their 2-dimensional images need to be interpreted in three dimensions. We have developed a Computer Assisted Tomography (CAT) program that modifies a three-dimensional heliospheric model to fit Thomson scattering solar minimum observations from the Helios spacecraft photometers. The tomography program iterates to a least-squares solution fit of observed brightness data using spacecraft and solar wind motion to provide perspective views of each point in space accessible to the observations. We plot the optimized models as Carrington maps in density for the Helios data sets. The results to date are commensurate with resolutions available from the original data. At solar minimum, longitudinally segmented dense structures emanate from near the solar equator. We explore the location of these dense structures with respect to the heliospheric current sheet and regions of activity on the solar surface.