High energy ions and electrons upstream from the Earth's bow shock and their dependence on geomagnetic conditions: Statistical results between years 1982–1988

Abstract

We present initial results from a statistical analysis of 2034 energetic (50–220 keV) ion events observed by the IMP‐8 spacecraft upstream from the Earth's bow shock during a 6 years period. The most important findings are the following: (1) the percentage Pe of high intensity energetic ion events accompanied by the presence of relativistic (≥ 220 keV) electrons is ∼80% (for all geomagnetic conditions), and increases significantly with increasing the index Kp of geomagnetic activity, (2) high intensity energetic ion events most often (∼93%) show spectra extending up to energies E>∼300 keV, (3) a percentage of ∼71.5% of events display non‐inverse energy dispersion of ion intensities. The above results, as well as additional results discussed in the text, suggest that a percentage as high as ∼80% of high intensity 50–220 keV ion events in our statistical sample have an origin within the magnetosphere.