A New Model of Solar Flares.
Abstract
A review of observational data concerning solar flares, including in particular data concerning homologous flares, leads to a statement of the principal requirements to be met by a flare model. It is submitted that earlier theories do not meet these requirements. A new model of solar flares is proposed in which the pre-flare state consists of a heavy mass of gas partially supported by a compressed magnetic field. Such a configuration is likely to form in those parts of the low chromosphere of a center of activity for which the magnetic field is nearly horizontal and for which the radius of curvature is directed upwards. The pre-flare state may have its origin in gas circulation due either to photo spheric temperature differences at a center of activity or to the nonthermal (acoustic) energy flux, or to a small vertical (upward) displacement of the magnetic field configuration. The instability appropriate to this configuration, to be identified with the flash phase of solar flares, is a gravitational resistive instability. This instability is sufficiently rapid, and it develops electric fields of sufficient magnitude to explain observed particle acceleration in solar flares. The instability also causes the plasma-field configuration to break up into fine filaments, in agreement with observations. This finescale structure effects a decoupling of the plasma and magnetic fields, permitting the overlying mass of gas to sink to the photosphere and the compressed magnetic field to relax to a force-free state; energy released in this phase corresponds to the main part of the light curve of a flare.
- Publication:
-
The Astronomical Journal
- Pub Date:
- 1965
- DOI:
- 10.1086/109651
- Bibcode:
- 1965AJ.....70S.331S