Extreme ultraviolet observation of mass flow in the low corona over a large sunspot.
Abstract
The authors have used an extreme ultraviolet (EUV) imaging spectrograph (SERTS) covering the spectral range from 235 to 450 Å to study velocity fields in the low solar corona. During a flight in May, 1989, they obtained emission line profile measurements along a chord through an active region on the Sun, including the corona over a sunspot and the initial stage of a small flare. Relative Doppler velocities were measured in the lines of Mg IX, Fe XV, and Fe XVI with a sensitivity of 2-3 km s-1 at 350 Å. The only significant Doppler shift observed was in the emission line of Mg IX at 368.1 Å over the umbra of the large sunspot. The maximum detected shift corresponded to a peak velocity toward the observer of 14±3 km s-1 relative to the mean of measurements in this emission line made elsewhere over the active region. The magnetic field in the low corona was aligned to within 10° of the line of sight at the location of maximum Doppler shift. Depending on the closure of the field, such a mass flow could either contribute to the solar wind or re-appear as a downflow of material in distant regions on the solar surface.
- Publication:
-
UV and X-ray Spectroscopy of Laboratory and Astrophysical Plasmas
- Pub Date:
- 1993
- Bibcode:
- 1993uxrs.conf..361N
- Keywords:
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- Solar Corona: UV Lines;
- Solar Corona: Extreme UV;
- Solar Corona: Mass Flow