ИСТИНА

Space observations of the Sun with high space, time and spectral resolution allows us to investigate quantitatively the phenomenon of magnetic reconnection in super-hot (with electron temperature higher 100 MK) plasmas in the solar corona and solar wind. Specific properties of large-scale reconnection in large solar flares are reviewed. A detail analysis and interpretation of topological features of large-scale magnetic fields in active regions shows that the effect of topological trigger is needed to be taken into account in order to model a large eruptive solar event with a coronal mass ejection (CME). A new class of analytical models of reconnection in current layers with attached MHD discontinuities is also presented. The problem of evolutionarity of these solutions is discussed. In order to describe propagation of the flare accelerated electrons in the solar atmosphere, a new accurate quantitative model of the so-called ``thick target’’ has been constructed. The model is based on the kinetic equation which takes into account Coulomb collisions of the accelerated electrons with thermal electrons and protons in the solar corona and chromospheres. The distribution function of accelerated electrons and the electric field of a reverse current have been found by self-consistent approach. The model is one-dimensional in an ordinary space but two-dimensional in the velocity space. The important consequence of this fact is that some electrons after injection into the thick target make a curve trajectory and cross the boundary in the reverse direction without significant losses of energy. Such a process is impossible in the models that are one-dimensional in the velocity space; for this reason they are non-physical approximations. New results on spectra and polarization of hard X-ray bremsstrahlung which arises during inelastic collisions of accelerated electrons with thermal ions in the solar atmosphere are presented. Open issues of the solar flare physics are briefly reviewed. Ref.: Somov B.V., Plasma Astrophysics, Part II, Reconnection and Flares, Second Edition, Springer SBM, N.Y., 2013.