Comparison of Tomographic and Forward Modeling 3D Reconstructions of a Coronal Streamer

We compare 3D reconstructions of a coronal streamer using two different techniques. Thernisien employs images from the LASCO coronagraph on board SOHO and determines the optimal parameter values of a general slab model (with folds) for electron density yielding a synthetic white light image that best matches the starting LASCO data (Thernisien et al. 2004, B.A.A.S., 36, 797). This forward modeling approach forces the solution to be of a pre-determined functional form. We compare this reconstruction with a true tomographic reconstruction using input images from multiple viewpoints, with no predetermined constraint on the geometry of the electron density distribution found. As an initial test of the tomographic reconstruction, we start with input synthetic coronagraph data rendered from the Thernisien model electron density reconstruction, and first compare the tomographic reconstruction to this known starting distribution. We next use true LASCO data from different days (rotational tomography) for a tomographic reconstruction, and compare the reconstructed electron density distribution and its rendered synthetic coronagraph data with the Thernisien electron densities and rendered coronagraph data. In general, with real data the tomographic reconstruction produces synthetic coronagraph images rendered from its electron density determination that are more similar to the input LASCO data, while the Thernisien electron density determination is more tightly structured, from its prior constraints, than the tomographic reconstruction from a very limited number of viewpoints. The two techniques are complementary, and both will provide useful reconstruction tools for use in the upcoming STEREO mission, due for launch in early 2006. JWC and JSN are supported on this work by NASA under W10135, and by the Office of Naval Research.