Title: Distortion of interplanetary pitch distributions by Earth's bow shock
Abstract: A theoretical study is made of the distortion of a given interplanetary pitch distribution when particles intercept the earth's bow shock. The behavior of energetic particles with gyroradius much larger than shock thickness, but smaller than a scale length for the magnetosheath geometry, is emphasized (this includes protons of energy 10 keV ≲ E ≲ 1 MeV). Scattering of pitch angles by small‐scale magnetic fluctuations is ignored. The distortion is studied at selected observing stations in both solar wind and magnetosheath. Substantial distortions occur when the interplanetary anisotropy is large. For a given ratio of maximum to minimum directional intensity in interplanetary space the distortion at certain stations depends on (1) the magnetic configuration and (2) the detailed shape of the interplanetary pitch distribution. Only when the bow shock is almost a perpendicular shock can the approximation of guiding center motion be employed with Liouville's theorem. Distorted pitch distributions in the magnetosheath are often characterized by a pronounced break, which can lie at positive, zero, or negative µ. Particle reflection from the bow shock sunward of earth is substantial. Some observations are presented which show trends that are consistent with the theoretical results. Over all, effects of the bow shock (at least sunward of earth) are serious, and particular care needs to be taken in inferring interplanetary pitch distributions and anisotropies from those measured by satellites near the earth.
Publication Year: 1978
Publication Date: 1978-12-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 8
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