Radial evolution of density structure in the solar corona

Abstract

White-light measurements made by the SOHO coronagraphs (LASCO for Large Angle Spectrometric Coronagraph) and the HAO Mauna Loa Mk III K-coronameter are combined to follow the evolution of path-integrated density structure in the solar corona overlying both coronal hole and quiet Sun regions from 1.15 to 5.5 Ro. The global imaging provided by these two instruments confirms and strengthens earlier results discovered by spacecraft radio ranging measurements [Woo and Habbal, 1999], that the imprint of density structure at the Sun - as manifested in the background latitudinal density profile closest to the Sun at 1.15 Ro - is carried essentially radially into interplanetary space with the same density gradient. The only exceptions are coronal streamers that evolve into the heliospheric current sheet within a few solar radii of the Sun. Copyright 1999 by the American Geophysical Union.