The properties of ionospheric O⁺ ions as observed in the magnetotail boundary layer and northern plasma lobe

Abstract

The ISEE 2 plasma experiment data are used to investigate the properties of the O + ions streams flowing in the earth's magnetotail low latitude boundary layer and northern plasma lobe. The E × B filter is seen to be the organizer of the flow of these ions, after their acceleration in the topside ionosphere. Between X SE =−15 R E and −23 R E the velocity of the O + ions is a function of the distance from the center magnetotail axis, the slower flowing closer to this and the faster closer to the magnetopause. The O + stream density is observed to vary with this distance as well. The temperature of the streaming ions is shown to be anisotropic with respect to the ambient magnetic field; a generally unresolved narrow conic pitch angle distribution of the O + ions is suggested to be the cause of this anisotropy. The properties of the O + ions are shown to be consistent with an acceleration mechanism, or a combination of mechanisms, that act orthogonally and parallel to the magnetic field.