Solar flare proton release from coronal magnetic traps and strong Alfvén turbulence in the corona

Drift instabilities arising when accelerated protons are trapped by coronal magnetic fields of active regions are investigated theoretically. If β, the ratio of total (plasma + energetic particles) pressure and magnetic field pressure is larger than some value, $\text{β?0.1}\text{to}\text{0.3}$, the magnetic trap is destructed and protons are released into interplanetary space. If $\text{β < β}{}^1$, the trapped protons excite gradient instability due to magnetic drift resonance. This “universal” instability results in rapid development of strong Alfvén wave turbulence with small wavelengths transverse to the magnetic field. Particle diffusion due to the waves has a rather complicated character and appears to be weak as compared to quasilinear diffusion. The role of Alfvén waves may consist in additional heating of the corona in the regions of closed magnetic field lines.     

Self-acceleration of nuclear flames in supernovae

The speed of the laminar flame in a degenerate carbon-oxygen white dwarf is too slow to produce a Type I supernova. We draw attention to the role of the Landau instability in wrinkling the flame front. This roughening of the front surface can cause an appreciable enhancement in the flame velocity. For typical presupernova conditions the density jump across the front is small. This implies the applicability of the potential approximation for describing the flow pattern and allows derivation of the Frankel equation for flame propagation. We report the results of our numerical experiments with this equation in a highly nonlinear regime. These calculations, coupled with analytic approximations allow us to determine the dependence of the fractal dimension of the front surface on the density jump across the front. Astrophysical implications of our results are discussed.