VIII. Theory of Solar Flares

Electron acceleration in solar flares: theory of spectral evolution

Context. Stochastic acceleration is thought to be a key mechanism in the energization of solar flare electrons. Aims. We study whether stochastic acceleration can reproduce the observed soft-hard-soft evolution of the spectral features of the hard X-ray emitted by suprathermal electrons. We pay special attention to the effects of particle trapping and escape. Methods. The Fokker-Planck equation...

Global Properties of Solar Flares

Lithium-6 from Solar Flares

By introducing a hitherto ignored Li producing process, due to accelerated He reactions with He, we show that accelerated particle interactions in solar flares produce much more Li than Li. By normalizing our calculations to gamma-ray data we demonstrate that the Li produced in solar flares, combined with photospheric Li, can account for the recently determined solar wind lithium isotopic ratio...

7Li PRODUCTION IN SOLAR FLARES

The Y ohkoh satellite has registered X-ray spectra of two solar Ñares with a linelike feature in the region 400È500 keV. Analysis shows that this feature can be interpreted as gamma-ray lines from excited 7Li and 7Be produced from a ] a reactions. The 7Li production rate in the solar atmosphere is estimated from these observations. The lower limit on the Ñare-produced 7Li abundance on the Sun i...

Solar flares and energetic particles.

Solar flares are now observed at all wavelengths from γ-rays to decametre radio waves. They are commonly associated with efficient production of energetic particles at all energies. These particles play a major role in the active Sun because they contain a large amount of the energy released during flares. Energetic electrons and ions interact with the solar atmosphere and produce high-energy X...