The viscous magnetopause

Cassen, P.; Szabó, J.

doi:10.1016/0032-0633(70)90173-x

Cited by 21 publications

(2 citation statements)

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“…Thus, the dawn magnetosheath flow may be intrinsically more variable than the dusk flow, resulting in the observed larger-amplitude magnetopause motion on the dawn side than on the dusk side. Within the framework of dissipational magnetohydrodynamics, Cassen and Szabo [1970] show that the boundary may be thin, as is predicted by dissipationless theory, but it may also occasionally be thick or 'disrupted.' Thus, the boundary layer thickness calculated from effective viscosities appears to be consistent within an order of magnitude with, though less than, our observed layer thickness of ~2…”

Section: Discussionmentioning

confidence: 76%

Magnetopause motions at lunar distance determined from the Explorer 35 Plasma Experiment

Howe¹,

Siscoe²

1972

J. Geophys. Res.

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From solar-wind plasma observations on the lunar orbiting Explorer 35 satellite, multiple boundary crossings have been analyzed to give statistical information on the tail boundary motions at lunar distance. In eleven months of observations, more than twice as many crossings occurred on the dawn side as on the dusk side, indicating a dawn-dusk asymmetry. The amplitude of boundary motion, given by the standard deviation of the observed positions around the average value, is 4.9 Rs on the dawn side and 2.8 Rs on the dusk side. Histograms of the time intervals between boundary crossings indicate two time scales are simultaneously present (16.7 min and 63.3 min, dawn-side values). A fit of the number of crossings and the histogram data to models of the motion indicates that the amplitude of the long-period motion is 2 to 3 times larger than that of the short-period motion. The inferred speeds for both motions lie in the range 10 to 20 km/sec. The models estimate the thickness of the plasma boundary layer to be 2 Since the flight of Explorer 10, which skirted the tail boundary in 1961, it has been known that the location of the boundary fluctuates [Bonetti et al., 1963; Heppner et al., 1963]. The fluctuation was confirmed subsequently by other space-probe traverses of the tail. With the launching of Explorer 35 began an opportunity for long-term monitoring of boundary locations at a fixed geometric distance (approximately 60 R•). Explorer 35 magnetic-field observations relating to the tail boundary have been reported [Mihalov et al., 1970], and they will be compared in a later section with the plasma observations given here. The plasma experiment on board the lunar orbiting spacecraft Explorer 35 measured plasma parameters from July 23, 1967, to July 14, 1968; during this time, the spacecraft made 11 complete traversals of the dawn and dusk magnetosheath. In general, each magnetosheath traversal included multiple encounters with the magnetopause, recognizable as the alternate appearance and disappearance of the directed solar-wind particle flux, and which we interpret Copyright (•) 1972 by the American Geophysical Union.as being due to magnetopause motion. On the basis of histograms of the time intervals between magnetopause encounters, we derive statistical parameters of the magnetopause motion at lunar distance, namely the characteristic amplitude and period.

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Section: Discussionmentioning

confidence: 76%