Double‐polytropic closure in the magnetosheath

L. ‐N Hau, T. ‐D Phan, B. U.Ö. Sonnerup, G. Paschmann

研究成果: 雜誌貢獻期刊論文同行評審

65 引文 斯高帕斯(Scopus)

摘要

The magnetosheath plasma is usually neither isotropic nor adiabatic. This paper contains an attempt to decribe its thermodynamic properties in terms of two polytropic laws, p⟂/ρBγ⟂−1 = C and pBγ∥−1 / ργ∥ = C, such that for γ = 2, γ = 3 the usual Chew‐Goldberger‐Low double‐adiabatic expressions are recovered and for γ = 1, γ = 1 double‐isothermal conditions are obtained. Using data from the AMPTE/IRM spacecraft, we show that the subsolar magnetosheath plasma may be better described by the double‐polytropic laws than by the mirror instability threshold, in particular in the low beta region near the magnetopause. The inferred polytropic exponents vary from event to event but are typically in the ranges of γ = 0.94 ± 0.10 and γ =1.14 ± 0.13 for the 29 cases we have examined.

原文???core.languages.en_GB???
頁(從 - 到)2255-2258
頁數4
期刊Geophysical Research Letters
20
發行號20
DOIs
出版狀態已出版 - 22 10月 1993

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