A New Model of Solar Flares

Abstract

view Abstract Citations (50) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Model of Solar Flares Sturrock, P. A. ; Coppi, B. Abstract Observational data concerning solar flares are reviewed briefly in order to list the salient requirements of a model of solar flares. The requirements of a theory of the flash phase are discussed in more detail, and previous flare theories are reviewed to determine the extent to which they meet these requirements. It is submitted that no theory meets enough of the requirements to be acceptable. A new model is proposed in which the preflare state consists of a mass of gas supported by a sheared magnetic field. This field configuration is likely to be met in the neighborhood of a fault line, across which there has been a shear displacement of the photosphere, since such a fault line tends to coincide with the dividing line between regions of opposite magnetic polarity. Such a configuration of gas and magnetic field is believed to be responsible for quiescent prominences, but the energy released in a flare is believed to come from lower parts of such a system, involving stronger fields and greater mass. This model there- fore explains the close relationship between flares and quiescent filaments. The flash phase of a solar flare is identified with a gravitational resistive instability of the above plasma-field configuration. It is shown that the rise time of this instability is sufficiently rapid to explain the very rapid development of the flash phase. The instability tends to break up the plasma into filaments with dimensions of a kilometer or less, in agreement with certain inferences which have been drawn from flare spectra. The development of fine-scale structure provides conditions for subsequent slower release of stored energy; this subsequent release is identified with the main or decay phase of flares. The flash-phase instability develops high current parallel to the magnetic field, which must be driven by an electric field parallel to the magnetic field. This permits one to identify the acceleration process in solar flares as runaway acceleration, and it is shown that this interpretation enables one to explain the observed energies of protons produced by solar flares. There is a brief discussion of the possibility of interpreting certain secondary flare phenomena, such as surges and loop prominences, by means of the proposed model. Publication: The Astrophysical Journal Pub Date: January 1966 DOI: 10.1086/148472 Bibcode: 1966ApJ...143....3S full text sources ADS |