OBSERVATIONS OF DETAILED STRUCTURE IN THE SOLAR WIND AT 1 AU WITH STEREO/HI-2

We present images of solar wind electron density structures at distances of 1 AU, extracted from the STEREO/HI-2 data. Collecting the images requires separating the Thomson-scattered signal from the other background/foreground sources that are 10(3) times brighter. Using a combination of techniques, we are able to generate calibrated imaging data of the solar wind with sensitivity of a few x 10(-17) B-circle dot, compared to the background signal of a few x 10(-13) B-circle dot, using only the STEREO/HI-2 Level 1 data as input. These images reveal detailed spatial structure in coronal mass ejections (CMEs) and the solar wind at projected solar distances in excess of 1 AU, at the instrumental motion-blur resolution limit of 1 degrees-3 degrees. CME features visible in the newly reprocessed data from 2008 December include leading-edge pileup, interior voids, filamentary structure, and rear cusps. "Quiet" solar wind features include V-shaped structures centered on the heliospheric current sheet, plasmoids, and "puffs" that correspond to the density fluctuations observed in situ. We compare many of these structures with in situ features detected near 1 AU. The reprocessed data demonstrate that it is possible to perform detailed structural analyses of heliospheric features with visible light imagery, at distances from the Sun of at least 1 AU.