Ion anisotropies in the outer Jovian magnetosphere
We present results from the Voyager 1 and 2 low-energy charged particle measurement of ion anisotropies in the outer Jovian magnetosphere (R> or approx. =20 R/sub J/). Theses anisotropies represent the first observed from an instrument rotating in the spin plane of Jupiter. For the several ion species ivestigated the first-order anisotropies are all strongly in the corotational sense throughout most of the Jovian magnestophere and out to the magnetopause on the dayside. There is some evidence for a small component of outward flow in the corotating region. Beyond approx.130--150 R/sub J/ along the Voyager outbound trajectories the anisotropies indicate a magnetospheric wind flowing outward from Jupiter. The change corotational to tailward flow on the nightside occurs well inside the magnetopause. The anisotropy amplitudes increase linearly with radial distance and, in the disc regions, decrease with distance from the magnetodisc mid-plane. In one case examined in detail using separtely identified H, He, and O/S ions the convection speed at 58 R/sub J/ is found to agree with the corotation speed (..cap omega..R) to within approx.3%. A linear Compton-Getting analysis reveals that the convective speeds in the dayside magnetosphere are in agreement with rigid corotation whenever the plasma flow direction is approximately in the corotation sense, while at other times the convection speeds are substantially less than corotation.
- Research Organization:
- John Hopkins Univ., Laurel, Maryland
- OSTI ID:
- 5788147
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 86:A10
- Country of Publication:
- United States
- Language:
- English
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