Observations of plasma depletion in the magnetosheath at the dayside magnetopause

Crooker, N. U.; Eastman, T. E.; Stiles, G. S.

doi:10.1029/ja084ia03p00869

Cited by 154 publications

(69 citation statements)

References 14 publications

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“…The latter serves as a further characterization of the layer, in addition to the f and x behaviour. Observational evidence for the PDL was ®rst reported by Paschmann et al (1978) and Crooker et al (1979). It has subsequently often been observed, and its properties studied, by AMPTE experimenters (Anderson et al, 1991;Paschmann et al, 1993;Phan et al, 1994;Phan and Paschmann, 1995).…”

Section: Introductionmentioning

confidence: 88%

MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985

et al. 1998

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Abstract. We compare numerical results obtained from a steady-state MHD model of solar wind¯ow past the terrestrial magnetosphere with documented observations made by the AMPTE/IRM spacecraft on 24 October, 1985, during an inbound crossing of the magnetosheath. Observations indicate that steady conditions prevailed during this about 4 hour-long crossing. The magnetic shear at spacecraft entry into the magnetosphere was 15. A steady density decrease and a concomitant magnetic ®eld pile-up were observed during the 40 min interval just preceding the magnetopause crossing. In this plasma depletion layer (1) the plasma beta dropped to values below unity; (2) the¯ow speed tangential to the magnetopause was enhanced; and (3) the local magnetic ®eld and velocity vectors became increasingly more orthogonal to each other as the magnetopause was approached (Phan et al., 1994). We model parameter variations along a spacecraft orbit approximating that of AMPTE/IRM, which was at slightly southern GSE latitudes and about 1.5 h postnoon Local Time. We model the magnetopause as a tangential discontinuity, as suggested by the observations, and take as input solar wind parameters those measured by AMPTE/IRM just prior to its bow shock crossing. We ®nd that computed ®eld and plasma pro®les across the magnetosheath and plasma depletion layer match all observations closely. Theoretical predictions on stagnation line¯ow near this low-shear magnetopause are con®rmed by the experimental ®nd-ings. Our theory does not give, and the data on this pass do not show, any localized density enhancements in the inner magnetosheath region just outside the plasma depletion layer.

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Section: Introductionmentioning

confidence: 88%

MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985

et al. 1998

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“…As ions can be heated in the perpendicular direction by the quasi-perpendicular bow shock , mirror mode structures are observed in the corresponding terrestrial magnetosheath (Kaufmann et al, 1970;Crooker et al, 1979;Tsurutani et al, 1982) and in the terrestrial cusp (Shi et al, 2009a). Observations and numerical simulations have shown that magnetic peaks are rarely seen in mirror stable plasma because of their rapid decay, but magnetic holes could survive in a mirror stable plasma.…”

Section: Introductionmentioning

confidence: 99%

Cluster and TC-1 observation of magnetic holes in the plasma sheet

Sun

Shi

et al. 2012

Ann. Geophys.

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Abstract. Magnetic holes with relatively small scale sizes, detected by Cluster and TC-1 in the magnetotail plasma sheet, are studied in this paper. It is found that these magnetic holes are spatial structures and they are not magnetic depressions generated by the flapping movement of the magnetotail current sheet. Most of the magnetic holes (93 %) were observed during intervals with B z larger than B x , i.e. they are more likely to occur in a dipolarized magnetic field topology. Our results also suggest that the occurrence of these magnetic holes might have a close relationship with the dipolarization process. The magnetic holes typically have a scale size comparable to the local proton Larmor radius and are accompanied by an electron energy flux enhancement at a 90 • pitch angle, which is quite different from the previously observed isotropic electron distributions inside magnetic holes in the plasma sheet. It is also shown that most of the magnetic holes occur in marginally mirror-stable environments. Whether the plasma sheet magnetic holes are generated by the mirror instability related to ions or not, however, is unknown. Comparison of ratios, scale sizes and propagation direction of magnetic holes detected by Cluster and TC-1, suggests that magnetic holes observed in the vicinity of the TC-1 orbit (∼7-12 R E ) are likely to be further developed than those observed by Cluster (∼7-18 R E ).

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“…This results in perpendicular compression of the field, a depletion of the total plasma density, and a temperature anisotropy ¹ , '¹ # (Crooker et al, 1979;Anderson and Fuselier, 1993;Zwan and Wolf, 1976). Thus the temperature anisotropy in this ''plasma depletion layer'' can drive Alfve´n/ion-cyclotron or mirror instabilities.…”

Section: The Magnetopause Itselfmentioning

confidence: 99%

Low-frequency waves in the Earth's magnetosheath: present status

1996

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Abstract. The terrestrial magnetosheath contains a rich variety of low-frequency (: proton gyrofrequency) fluctuations. Kinetic and fluid-like processes at the bow shock, within the magnetosheath plasma, and at the magnetopause all provide sources of wave energy. The dominance of kinetic features such as temperature anisotropies, coupled with the high-conditions, complicates the wave dispersion and variety of instabilities to the point where mode identification is difficult. We review here the observed fluctuations and attempts to identify the dominant modes, along with the identification tools. Alfve´n/ioncyclotron and mirror modes are generated by ¹ ,

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Observations of plasma depletion in the magnetosheath at the dayside magnetopause

Cited by 154 publications

References 14 publications

MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985

MHD model of magnetosheath flow: comparison with AMPTE/IRM observations on 24 October, 1985

Cluster and TC-1 observation of magnetic holes in the plasma sheet

Low-frequency waves in the Earth's magnetosheath: present status

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