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GEOS-2 Measurements of Cold Ions in the Magnetosheath

Document Type

Article

Journal/Book Title/Conference

Planetary and Space Science

Volume

33

Issue

6

Publication Date

1985

First Page

675

Last Page

684

Abstract

The Suprathermal Plasma Analysers on GEOS-2 are able to make differential energy measurements of plasma particles down to sub-eV energies because the entire sensor package can be biased relative to the spacecraft. When the package is biased negatively with respect to space potential, low energy positive ions are sucked in and are more easily detected against the background. Large fluxes of ions with temperatures of the order of 1 eV or less were consistently detected at space potential when the spacecraft was in the magnetosheath though not when it was in the nearby magnetosphere. This apparent geophysical correlation, suggesting that the ions were part of the magnetosheath ion population, was contradicted by the fact that the ions showed no signs of the large drift velocity associated with the electric field in the magnetosheath. We conclude, after further investigation, that the observed ions were probably sputtered as neutrals from the spacecraft surface by the impact of solar wind ions and subsequently ionized by sunlight or electron impact. The effect of sputtering by solar wind ions has not been previously observed, although it could have consequences for the long-term stability of spacecraft surfaces.

Comments

Originally published by Elsevier. Publisher’s PDF available through remote link.

https://doi.org/10.1016/0032-0633(85)90049-2

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