Origin and development of solar flares
Abstract
A review is given of knowledge on solar flares with particular emphasis on progress made during the international Solar Maximum Year (1979-1981). The pre-flare structure is described by a flux-tube or circuit model. The instability leading to a flare may occur by a disturbance of the field topology (mostly field emergence) followed by field-line reconnection (circuit coupling). In the first (impulsive) phase of a flare, this causes jets of energetic electrons originating near the top of the flux tube to bombard lower chromospheric regions: footpoint heating. In the second (gradual or diffuse) phase, heated gas from the footpoints ascends convectively, producing a large cloud of hot gas. Consequent shock-wave phenomena cause moving fronts and associated waves in the high parts of the corona; these show up in coronagraphic or radio-observations. Several hours after a large flare, extended loop-like structures can appear, with temperatures greater than 6 MK, emitting a very faint X-ray flux. They are the basic structures of a more extended configuration, visible on metric radio waves, and pointing out from the area where the flare occurred. They may extend to distances of 10 to the 6th km or more from the solar surface.
- Publication:
-
Highlights of Astronomy
- Pub Date:
- 1983
- Bibcode:
- 1983HiA.....6...53D
- Keywords:
-
- Plasma Acceleration;
- Solar Flares;
- Solar X-Rays;
- Coronal Loops;
- Magnetic Flux;
- Plasma Currents;
- Solar Magnetic Field;
- Solar Physics