POLAR RAIN: SOLAR CORONAL ELECTRONS IN THE EARTH'S MAGNETOSPHERE.

Abstract

The paper describes ISEE 1 measurements of anisotropic, field-aligned, tail lobe electrons whose occurrence characteristics identify them as the tail lobe component of the electron distribution function that precipitates as polar rain. The authors then examine the question of solar wind origin of the polar rain using contemporary knowledge of anisotropic solar wind distribution functions that was not available at the time of earlier magnetospheric measurements. By mapping these distribution functions along field lines between the solar wind and the tail lobe, it is quantitatively demonstrated that the polar rain is indeed of solar wind origin with the north-south asymmetry due to the previously unknown anisotropic component of the solar wind: the strahl. Refs.