Loop models of solar flares: Revisions and comparisons

Abstract

Due to developments in solar flare observations which appear to show that a particular class of solar flares result from instabilities occurring in magnetic loops we re-examine the Alfv6n-Carlqvist flare model to show that it is workable and we update the Spicer loop model of a flare. It is noted that the Alfv6n-Carlqvist model of necessity requires an external current driver which must maintain the current driven instability at marginal stability during the duration of the flare. In addition, it is argued that if the Alfv6n-Carlqvist model is to work the current density must rise in a time shorter than an MHD or resistive tearing mode time scale. Otherwise, the dominant flare mechanism must be an ideal MHD or tearing type instability. Further, the distinctions between the two models are highlighted and a new hybrid model of the Alfv6n-Carlqvist and Spicer models is introduced.

Very Large Array Observations of Coronal Loops and Related Observations of Solar Type Stars.

“…The poorer angular resolution of single antennas would combine the signals from different sources, and the cyclotron lines might be lost in the superposition of the different sources which radiate at different frequencies. Tw - (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) x 10" K of the 20 cm bursts are similar to those (0 > I") and moderate time resolution (r t 10 s) have proobserved at soft X-ray wavelengths. In k IIl we discuss the vided new insights into the physics of solar radio bursts.…”

“…More recent 21 cm VLA observations by * showed evidence for preburst heating and magnetic field changes in burst sources that were spatially separated from the sites of the impulsive sources. These radio wavelength results are similar to those that have been detected at X-ray wavelengths in which adjacent loops brighten and perhaps trigger the eruption of other bursts (Vorpahl et al, 1975;Kahler etal., 1975;Kahler etal., 1976 and then erupts, giving rise to the impulsive phase Spicer, 1981;Somov and Syrovatskii, 1982). High resolution observations of the preburst evolution of coronal loops may therefore place useful constraints on these models as well as allow comparisons with other preflare phenomena, such as filament eruption, preflare vortical structure, Hot and X-ray brightening and coronal transients, for which direct association with flares has been implied (cf.…”

Particle Acceleration Processes in the Solar Corona

“…also Pritchet, Lee and Drake (1980). The concept of tearing modes was incorporated into a flare model by Spicer (1977Spicer ( , 1981Spicer ( , 1982. In a model of magnetic energy dissipation based of tearing modes, the magnetic energy is released at a large number of localised sites associated with magnetic islands, as illustrated schematically in Fig.…”

Multiple energetic injections in a strong spike-like solar burst

“…The mechanism, based on magnetohydrodynamic conditions described by Forth et-al. , (1963), was recently analysed by Spicer (1981). Initial reconnections can generate primary magnetic islands.…”