Magnetosheath electrons in anomalously low density solar wind observed by Geotail

Abstract

We present an overview of the magnetosheath electron observations above 60 eV in the anomalously low density solar wind on 11 May 1999 observed by Geotail. We observed anisotropic ‘strahl’ component not only in the solar wind but also in the magnetosheath. Strahl is observed during the interval of 6–21h UT and most enhanced in the interval surrounding the solar wind density minimum in 18–19h UT. Its temperature seems positively correlated to its flux. We also evaluate the density and temperature of low energy isotropic component. The variation of density is associated with proton density. Its temperature is continuous, and suddenly decreased after the density minimum in ∼18–19h UT. We also compared our downstream data with upstream one observed by the ACE spacecraft. We conclude that the electron acceleration and heating at the bow shock is executed in the ordinal mechanisms even in the low density solar wind.