Boris V. Somov 
Plasma Astrophysics, Part II 
Reconnection and Flares

Magnetic ?elds are easily generated in astrophysical plasma owing to its ?6 high conductivity. Magnetic ?elds, having strengths of order few 10 G, correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to ampli?cation of a small seed ?eld by a turbulent galactic dynamo. In several galaxies, like the famous M51, magnetic ?elds are well correlated (or anti-correlated) with the optical spiral arms. These are the weakest large-scale ?elds observed in cosmic space. The strongest magnets in space are presumably the so-called magnetars, the highly mag- 15 netized (with the strength of the ?eld of about 10 G) young neutron stars formed in the supernova explosions. The energy of magnetic ?elds is accumulated in astrophysical plasma, and the sudden release of this energy – an original electrodynamical ‘burst’ or‘explosion’–takesplaceunderde?nitebutquitegeneralconditions(P- att, 1992; Sturrock, 1994; Kivelson and Russell, 1995; Rose, 1998; Priest and Forbes, 2000; Somov, 2000; Kundt, 2001). Such a ‘?are’ in ast- physical plasma is accompanied by fast directed ejections (jets) of plasma, powerful ?ows of heat and hard electromagnetic radiation as well as by impulsive acceleration of charged particles to high energies.

Table of Content

Plasma Astrophysics.- Particles and Fields: Exact Self-Consistent Description.- Statistical Description of Interacting Particle Systems.- Weakly-Coupled Systems with Binary Collisions.- Propagation of Fast Particles in Plasma.- Motion of a Charged Particle in Given Fields.- Adiabatic Invariants in Astrophysical Plasma.- Wave-Particle Interaction in Astrophysical Plasma.- Coulomb Collisions in Astrophysical Plasma.- Macroscopic Description of Astrophysical Plasma.- Multi-Fluid Models of Astrophysical Plasma.- The Generalized Ohm’s Law in Plasma.- Single-Fluid Models for Astrophysical Plasma.- Magnetohydrodynamics in Astrophysics.- Plasma Flows in a Strong Magnetic Field.- MHD Waves in Astrophysical Plasma.- Discontinuous Flows in a MHD Medium.- Evolutionarity of MHD Discontinuities.- Particle Acceleration by Shock Waves.- Plasma Equilibrium in Magnetic Field.- Stationary Flows in a Magnetic Field.- Reconnection and Flares: Introduction.- Magnetic Reconnection.- Reconnection in a Strong Magnetic Field.- Evidence of Reconnection in Solar Flares.- The Bastille Day 2000 Flare.- Electric Currents Related to Reconnection.- Models of Reconnecting Current Layers.- Reconnection and Collapsing Traps in Solar Flares.- Solar-type Flares in Laboratory and Space.- Particle Acceleration in Current Layers.- Structural Instability of Reconnecting Current Layers.- Tearing Instability of Reconnecting Current Layers.- Magnetic Reconnection and Turbulence.- Reconnection in Weakly-Ionized Plasma.- Magnetic Reconnection of Electric Currents.- Epilogue.