Three-dimensional Tomographic Analysis of a High-Cadence LASCO-C2 Polarized Brightness Sequence

Abstract

We present the first 3D tomographic reconstructions of the coronal electron density from an extended, high-cadence sequence of images of the corona's polarized brightness (pB). While the standard LASCO synoptic sequence is only 1 pB image per day, during the 14 day period covering 2006 June 9-22, the C2 coronagraph took about 6.5 pB images per day. We show that the high cadence dramatically improves the quality of the tomographic reconstructions when compared to a reconstruction that only uses one image per day. In particular, the reconstruction that uses only one image per day misses important features and has lower spatial resolution. We find that the spatial resolution of the tomographic inversion is ultimately limited by smearing due to coronal dynamics that take place during the 14 days required for data acquisition. We show that when only C2 images are available, about 4 pB images per day are enough for nearly optimal tomographic reconstruction, but more will be required when STEREO observations are included in the tomographic analysis.