Three-dimensional energetic ion observations and the tangential magnetopause electric field

Abstract

Three-dimensional distributions for 24.0–44.5 keV protons (ions) are presented from the ISEE-1 medium energy particles instrument during a magnetopause traversal at ∼ 01:10 UT on 20 November 1977. Local time of the traversal was ∼10∶30. Ion fluxes were observed coming generally from the subsolar region, but over a wide range of latitudes. Enhanced fluxes were observed at the magnetopause crossing with strong components from the subsolar region and from the +Z _SE direction. These observations are compared with the simultaneous electric field observations presented by Mozer et al. (1978). Ion streaming in a direction consistent with the Y-component of the $E x B/_{B^2 }$ drift velocity was observed whereas streaming along the X and Z-components is not seen. Based on energy arguments we conclude that in this case, ⩾24 keV ions are not the major energy carrier of the locally measured Ī · Ē dissipation.