Some problems of magnetosheath physics

A short discussion of some problems of magnetosheath physics is presented. In particular, we consider various models of the proton temperature anisotropy evolution across the magnetosheath and the problem of the proton pitch-angle diffusion rate. The value of the characteristic relaxation time ( tau ) of the proton temperature anisotropy is estimated from experimental data. The obtained values of tau and their variations across the magnetosheath require a theoretical explanation, which is at present unattainable due to the absence of a sufficiently developed non-linear theory of the plasma wave turbulence necessary for estimates of the intensity of the latter. Another problem considered in the review concerns the conditions of formation of a magnetic barrier within the magnetosheath. The existing controversy in this question is explained in the authors' opinion by a different definition of the term "magnetic barrier" used in papers by Pudovkin et al. [1982, 1995] and Phan et al. [1994]. It follows that experimental data presented in papers by these two groups reasonably complement each other rather than contradict. Through combined results of investigations carried out by these groups, one can follow the variation of the magnetic field intensity and plasma density across the entire magnetosheath, including the bow shock and the transition layer within the magnetopause.