Asymptotic Theory of Solar Wind Electron Halo Distribution

Friday, 19 December 2014
Sunjung Kim, Kyung Hee University, Yongin, South Korea and Peter Haesung Yoon, Univ Maryland, College Park, MD, United States
The solar wind electrons are conveniently divided into core Maxwellian background, isotropic halo, and super-halo components (and some times, highly field-aligned strahl component, which can be considered as a fourth element). Recently, a theory was proposed that explains the origin of super-halo distribution. It was assumed that the super-halo distribution forms as a result of wave-particle interaction between the super-halo electron and steady-state Langmuir fluctuation known as the quasi-thermal noise. In the present paper, we discuss a theory of solar wind halo electron distribution. It is assumed that the solar wind electrons whose energy is intermediate to the Gaussian cold core and super-halo components can interact efficiently with the whistler turbulence, which is pervasively detected in the solar wind near 1 AU. By making use of Fokker-Planck particle kinetic equations for the electrons and the wave kinetic equation for the whistler waves, it is shown that the solar wind halo distribution emerges as an asymptotic steady-state solution. The figure shown below summarizes the theoretical reconstruction of the total solar wind electron velocity distribution.