Average plasma-sheet configuration near 60 Earth radii

Meng, C.‐I.; Mihalov, J. D.

doi:10.1029/ja077i010p01739

Cited by 42 publications

(20 citation statements)

References 28 publications

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“…This implies that the plasma sheet must be thicker at the sides than at the center of the tail. The results of Bame et al [ 1967], which suggest that this is the case, have been confirmed by Meng and Mihalov [1972a], and on the basis of this latter study we estimate that/ the plasma sheet thickness increases from about 5 R• near the center of the tail to about l0 R• near the flanks (viz., (a/b) •. • in Figure 6).…”

Section: The Model: a Quantitative Treatmentsupporting

confidence: 88%

A mechanism for driving the gross Birkeland current configuration in the auroral oval

Rostoker¹,

Boström²

1976

J. Geophys. Res.

140

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Birkeland (field‐aligned) sheet currents flowing into and out of the auroral oval as reported by Zmuda and Armstrong (1974) are integrally associated with convective motion of plasma in the magnetotail. It is demonstrated that these currents can be driven by energy supplied by the braking of this convective motion of the plasma sheet particles as they drift toward the flanks of the magnetosphere. In the ionosphere the sheet currents close as Pedersen currents, resulting in the dissipation of power, while far from the earth the closure currents, which provide the braking force for the plasma, flow in the plasma sheet approximately normal to the neutral sheet out to radial distances of about 80 RE. During periods of moderate magnetospheric activity the Birkeland currents result in a rate of dissipation of convective energy of the order of 10 GW.

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Section: The Model: a Quantitative Treatmentsupporting

confidence: 88%

A mechanism for driving the gross Birkeland current configuration in the auroral oval

Rostoker¹,

Boström²

1976

J. Geophys. Res.

140

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“…Thus in the following discussion it is assumed that even if the solar wind were perfectly The plasma sheet in some form extends at least as far as the lunar orbit at 60-RE distance. The shape of the plasma sheet at lunar distance inferred from magnetometer measurements is similar to that at the Vela orbit [Meng and Mihalov, 1972]. The plasma sheet thickness at 60 RE is roughly half of that at 18 RE, and the energy density is down by about a factor of 5, owing to decreases both in density and in temperature [Rich et al, 1973].…”

supporting

confidence: 52%

Origin of the plasma sheet

Hill¹

1974

Reviews of Geophysics

113

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The plasma sheet is a region of hot plasma (∼107 °K) that surrounds the earth, filling the distant magnetosphere and separating the northern and southern lobes of the magnetospheric tail; its origin is one of the basic outstanding problems of magnetospheric physics. A critical review of the available observations indicates that the plasma sheet source must provide roughly 1025–1026 particles/s to balance known loss mechanisms operating in the quiet time magnetosphere and that an adiabatic or quasi‐adiabatic (ΔE ∝ E) acceleration mechanism must provide most of the observed particle energy. These constraints together with auroral helium ion measurements indicate that the plasma sheet particles must originate in the solar wind rather than in the terrestrial ionosphere. The available hypotheses for a solar wind source are examined, and it is concluded that a two‐step process of magnetopause diffusion plus electrostatic acceleration is the simplest source mechanism that is consistent with the available observations.

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“…Satellite observations indicate that the thickness of the neutral sheet in the undisturbed geomagnetic tail is of the order of 1 Rr, while the plasma sheet thickness is 5-8 R• [Speiser and Ness, 1967;Mihalov et al, 1970;Meng and Mihalov, 1972]. The magnetic field in the lobes of the tail decreases from ~19 7 at ~20 R• to ~10 7 at ~60 Rr [Behannon, 1968;Mihalov and Sonerr, 1968].…”

mentioning

confidence: 99%

On the structure of the magnetotail current sheet

Kan¹

1973

J. Geophys. Res.

152

118

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A self-consistent tail current sheet model described by an exact analytic solution of the time independent Viasoy-Maxwell equations is presented. The model has a 'slingshot' field configuration with field lines outside the plasma, .sheet slightly flared in the antisolar direction. It is pointed out that when the model parameters are adjusted to agree with the spatial variation along the tail the required thickness of the neutral sheet must be •2.5 Rr, instead of _•1 Rr as indicated by observations. Furthermore, it is shown qualitatively that a considerable velocity shear must be present in the tail current sheet if the plasma sheet is indeed much thicker than the neutral sheet. Satellite observations indicate that the thickness of the neutral sheet in the undisturbed geomagnetic tail is of the order of 1 Rr, while the plasma sheet thickness is 5-8 R• [Speiser and Ness, 1967; Mihalov et al., 1970; Meng and Mihalov, 1972]. The magnetic field in the lobes of the tail decreases from ~19 7 at ~20 R• to ~10 7 at ~60 Rr [Behannon, 1968; Mihalov and Sonerr, 1968]. The field component perpendicular to the neutral sheet also decreases along the tail; e.g., B z ~ 3.52 7 at ~20 Rr and decreases to ~0.55 7 at ~60 R• [Behannon, 1970]. Recently, Siscoe [1972] and Rich et al. [1972] concluded, based on the stress balance condition, that either the true B z is much smaller than the reported average value (3.52 7 at 20 R•) or the neutral sheet is much thicker than 1 R• or the pressure in the plasma sheet is anisotropic with P• > Pl or there is a substantial plasma flow in the quiet tail. A similar conclusion has been reached independently by Cole and Schindler [1972]. On the other hand, Bird and Beard [1972] calculated a tail current system based on the first-order guiding center theory and claim that their results are in close accord with the observed plasma sheet and neutral sheet thicknesses. However, their definition of the neutral sheet thickness is different from the definition used in some observations [e.g., Mihalov et al., 1970]. Soop aad Schindler [1972] presented a general discussion of a self-consistent current sheet for magnetospheric structures. In this paper we present a quantitative dis-Copyright ¸ 1973 by the American Geophysical Union. cussion of the tail current sheet based on an analytic equilibrium solution (O/Ot --0) of the Vlasov-Maxwell equations. This solution describes a 'slingshot' field configuration with field lines outside the plasma sheet slightly flared in the antisolar direction. If the reported field variation along the tail and the reported field magnitudes are adopted, the present model admits a neutral sheet with thickness 2h ~ 2.5 Rr, which is. somewhat large compared with the observed value (2h •< 1 Rr). In this sense, our results confirm the qualitative conclusions of Siscoe [1972], Rich et al. [1972], and Cole and Schindler [1972]. Furthermore, it will be shown that for a given neutral sheet thickness the plasma sheet can be made thicker than the neutral sheet by introducing a velocity shea...

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Average plasma-sheet configuration near 60 Earth radii

Cited by 42 publications

References 28 publications

A mechanism for driving the gross Birkeland current configuration in the auroral oval

A mechanism for driving the gross Birkeland current configuration in the auroral oval

Origin of the plasma sheet

On the structure of the magnetotail current sheet

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