Plasma Astrophysics, Part II

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.