Simulation of asymmetric solar wind electron distributions

The electron distributions detected in the solar wind feature varying degrees of anisotropic high-energy tail. In a recent work the present authors numerically solved the one-dimensional electrostatic weak turbulence equations by assuming that the solar wind electrons are initially composed of thermal core plus field-aligned counterstreaming beams, and demonstrated that a wide variety of asymmetric energetic tail distribution may result. In the present paper, the essential findings in this work are tested by means of full particle-in-cell simulation technique. It is found that the previous results are largely confirmed, thus providing evidence that the paradigm of local electron acceleration to high-energy tail by self-consistently excited Langmuir turbulence may be relevant to the solar wind environment under certain circumstances. However, some discrepancies are found such that the nearly one-sided energetic tail reported in the numerical solution of the weak turbulence kinetic equation is not shown.