On the existence of non-Maxwellian velocity distribution functions in the corona and their consequences for the solar wind acceleration

Abstract

Non-thermal electron and ion velocity distribution functions are permanently observed in the solar wind. The exact origins of such departures from equilibrium Maxwell-Boltzmann distributions remain unclear. It is however believed that the rarity of Coulomb collisions in most of the extended corona and solar wind plays a crucial role in the mechanisms which produce and/or maintain such distributions. In this paper we focuss more on the electron distribution functions. We summarize their various observations and discuss about their possible coronal origin and role in the Solar Wind acceleration processes. © 2007 Springer.