Continual Expansion of the Active-Region Corona Observed by the YOHKOH Soft X-Ray Telescope
Abstract
We have found from the observations of the Yohkoh Soft X-ray Telescope (SXT) that the corona above active regions expands occasionally, and almost continually in the cases of ``active" active regions. This is contrary to the commonly accepted idea of magnetohydrostatic equilibrium of these regions. The key to this discovery has been a movie representation of the Yohkoh-SXT data, which, for the first time, provides adequate sampling and continuity for this purpose. The movies show ubiquitous expansions above the active regions, with velocities in the range of a few to a few tens km s(-1) as measured when they are on the limb. The expansion appears to preserve the overall structure of the active-region corona. We suggest that the expansion may have a physical relationship with the transient loop brightenings found within the active regions. This finding of almost continual expansion of the active-region corona may affect some of the basic ideas concerning active regions, as well as those of the mass-loss from the Sun and Sun-like stars.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- October 1992
- Bibcode:
- 1992PASJ...44L.155U
- Keywords:
-
- Solar Activity;
- Solar Corona;
- Spaceborne Telescopes;
- X Ray Telescopes;
- Japanese Spacecraft;
- Solar X-Rays;
- Solar Physics;
- SUN: ACTIVE REGIONS;
- SUN: CORONA;
- SUN: X-RAYS