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| Titel |
Electromagnetic proton cyclotron instability: heating of cool magnetospheric helium ions |
| VerfasserIn |
S. Peter Gary, Lin Yin, Dan Winske |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 1 ; Nr. 14, no. 1, S.1-10 |
| Datensatznummer |
250012131
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| Publikation (Nr.) |
 copernicus.org/angeo-14-1-1996.pdf |
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| Zusammenfassung |
| The electromagnetic proton cyclotron
anisotropy instability is excited if the hot proton temperature anisotropy, T⊥h/T\mid\mid
h, is sufficiently large compared to unity, where the subscript h
denotes the hot protons and the perpendicular and parallel symbols denote
directions relative to the background magnetic field. This instability is
important in the outer magnetosphere because it has been shown to lead to an
upper bound on T⊥h/T\mid\mid
h and to cool iron heating. Here one-dimensional initial-value
hybrid simulations with spatial variations in the direction of the background
magnetic field are used to study this instability in a homogeneous plasma model
which represents three ionic constituents of the outer magnetosphere: hot
anisotropic protons, cool, initially isotropic protons, and cool, initially
isotropic singly ionized helium. These simulations show that the presence of a
tenuous helium component does not significantly change the scalings of either
the hot proton anisotropy upper bound or the heating of the cool protons. The
simulations also show that the helium ion heating rate increases with
β\mid\midh in contrast to the cool
proton energization which decreases with this parameter. The prediction of this
homogeneous plasma model, therefore, for cool ions subject to heating by the
proton cyclotron instability is that the observed ratio of cool helium
temperature to cool proton temperature should increase as β\mid\midh
increases. |
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