On statistical acceleration of particles near Venus

Various gasdynamic and kinematic problems of the solar wind interaction with the ionosphere of Venus on the dayside are investigated. On the assumption that in the transition region between the bow shock and ionopause there exists an irregular magnetic field of B ≈ 20 nT, we estimate typical plasma parameters such as: mean free path, internal scale of inhomogeneities, viscosities, plasma conductivity and dissipated energy. A statistical acceleration mechanism in the transition region is investigated. We find that protons are accelerated in time at a rate proportional to t ^{2 3} up to an energy of approximately keV, and their distribution function is n(E) ∝ E ^{1 2}; n(ν) ∝ ν². The acceleration of electrons up to relativistic energies is proportional to the acceleration time. Heavy ions are also subject to acceleration and the mechanism appears able to explain the observed phenomena.