IPST, University of Maryland
Understanding the Origin of Non-Maxwellian Charged-Particle Distribution in Space
Charged particle acceleration takes place ubiquitously in the Universe including the near-Earth heliospheric environment. Typical in situ spacecraft measurements made in the solar wind show that the charged particle velocity distribution contains energetic components with quasi scale-free power-law velocity dependence, f ~ v−a, for high velocity range. In this talk a theory of quiet-time solar-wind electrons that contain a suprathermal component is discussed, in which these electrons are taken to be in dynamical equilibrium with Langmuir turbulence. Theoretical predictions of high-energy electron velocity power-law distribution index is then compared against the recent observations of the superhalo electron velocity distribution made by instruments onboard WIND and STEREO spacecraft. It is shown that the theoretical prediction of velocity power-law index is intermediate to the observed range.