Coordinated observations of the quiet Sun transition region using SUMER spectra, TRACE images and MDI magnetograms

TitleCoordinated observations of the quiet Sun transition region using SUMER spectra, TRACE images and MDI magnetograms
Publication TypeJournal Article
Year of Publication2001
AuthorsInnes, D. E.
JournalAstronomy and Astrophysics
Volume378
Pagination1067-1077
Date PublishedNov
Abstract

The relationship between the transition region ultraviolet emission and the underlying magnetic field is explored through a detailed analysis of SUMER SI IV line profiles, TRACE C IV, continuum and 171 Å intensities, and MDI high resolution magnetic field measurements. The observations track a narrow area of quiet Sun near disk center over a period of 3 hours. Highly variable emission is found throughout. The most dramatic line Doppler shift and brightness variations come from a region of complex field evolution. The brightenings sometimes have faint elongated extensions in the TRACE C IV images. In most events with high Doppler shifts, the SI IV line wing reveals plasma flow 1-2 min before the line core brightens which suggests that plasma acceleration precedes plasma compression and/or heating. SImultaneous measurement of transition region densities using O IV line ratios imply large density fluctuations in the transition region plasma. There is an indication of waves of compression and rarefaction crossing the spectrometer's field-of-view. The waves' speed across the solar surface is between 20-40 $\backslash$kms, and the compression may be as high as 10. In space-time images density fluctuations are much more prevalent and conspicuous than brightenings. In several cases the waves seem to start at the position of SI IV brightenings.

DOI10.1051/0004-6361:20011177