Investigating the Nonthermal Velocity of Small GOES-Class Flares Observed by Yohkoh
Abstract
Previous examinations of line broadening in solar flares have tended to concentrate on large GOES (Geostationary Operational Environmental Satellite) classification events. Because of the sensitivity of the Yohkoh Bragg crystal spectrometer, it is possible to observe small GOES flares. We derive the nonthermal velocity for 45 small GOES flares observed during 1994 by Yohkoh, concentrating on the peak and rise phase of the nonthermal velocity (Vnt). We examine the variation of Vnt with electron temperature, GOES classification, duration of event, rise time, and the source size of the event. The results demonstrate that the broadening is independent of the flare size, complexity, and intensity of hard X-ray bursts. There is a weak dependence on duration and rise time: as the durations and rise times become longer, the value of Vnt decreases. There is also a trend of increasing Vnt with increasing temperature for the same ion.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1997
- DOI:
- 10.1086/303857
- Bibcode:
- 1997ApJ...479..464H
- Keywords:
-
- Line: Profiles;
- Sun: Flares;
- Sun: X-Rays;
- Gamma Rays