Evaporation in the Transition Region during the Gradual Phase of Flares
Abstract
Previous observations have revealed that small, but sustained, H-alpha blueshifts occur in flare ribbons during the gradual, or late, phase of flares. These blueshifts suggest that there is a gentle evaporation of chromospheric material throughout the late phase of flares, but ambiguities in the interpretation of H-alpha leave open the possibility that these blueshifts are caused by downflowing, rather than upflowing, material. Using both C IV and soft (3.5-8 keV) X-ray data from SMM observations, evidence is found which supports the interpretation of the H-alpha blueshifts as upflows in the range from 4-12 km/s. The blueshifts are interpreted in terms of the reconnection model proposed by Carmichael (1964). The model produces a sustained energy release through-out the late phase which accounts for the prolonged soft X-ray emission after a flare. This energy release comes from the reconnecting magnetic field above the flare site, and some of the energy is transported along field lines mapping to the chromosphere where it drives chromospheric evaporation.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1990
- DOI:
- 10.1086/168879
- Bibcode:
- 1990ApJ...356..720S
- Keywords:
-
- Evaporation;
- Magnetohydrodynamics;
- Solar Flares;
- Solar Radiation;
- Solar Spectra;
- Solar X-Rays;
- Chromosphere;
- H Alpha Line;
- Lines Of Force;
- Magnetic Field Reconnection;
- Solar Physics;
- HYDROMAGNETICS;
- SUN: FLARES;
- SUN: SPECTRA;
- SUN: TRANSITION REGION;
- SUN: X-RAYS