Large‐Scale Coronal Density and Abundance Structures and Their Association with Magnetic Field Structure

Abstract

We construct subsynoptic maps of the ultraviolet-line fluxes, electron density, and elemental abundances for an east limb corona at 1.63 solar radii from 2000 September 20 to October 1. The data, covering position angles of 85°-126°, were taken from the Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO), and the maps are based on the variation of these parameters along the field of view of the UVCS slit. Combining these maps with the limb synoptic maps made from SOHO Extreme Ultraviolet Imaging Telescope, SOHO Large Angle and Spectrometric Coronagraph, and Yohkoh Soft X-ray Telescope observations provides a large-scale, distinct view of the contrast between different coronal structures in different physical properties and their relation to the underlying disk and magnetic field structures. During this time period, the east limb corona mainly consisted of three streamers and two dark areas that exhibited very different plasma properties. We construct a three-dimensional MHD coronal model that incorporates energy transport processes, and compare the large-scale coronal properties of the model with those of the observation. The comparison investigates areas of different abundances and densities, and their possible association with open and closed magnetic field structures. We find a good indication that the open field regions, which we believe to be the slow-wind source regions in this case, have lower coronal density and higher abundance values than the closed field regions. This is true for absolute abundance, and probably also for the FIP bias. Therefore, such synoptic maps can be very useful for identifying solar wind source regions.