Study of energetic particle anisotropy in weak and strong foreshocks Original Research Article

In this paper, we continue our recent statistical studies of solar wind plasma fluctuations in the Earth’s foreshock and their relationship to measurements of energetic ion (∼25, 50, 110 keV energy channels) fluxes under different solar wind and interplanetary magnetic field conditions, based on the INTERBALL–1 data obtained during 1995–2000. We discuss spatial and temporal characteristics of the energetic particle interaction with the foreshock plasma. We compare the intervals of upstream observations inside the foreshock of different strengths and relate plasma fluctuations to observed energetic particle pitch-angle distributions, anisotropy, and spectra at different distances to the bow shock. We discuss possible physical explanations of observed phenomena.