Polytropic index of central plasma sheet ions based on MHD Bernoulli integral

Pang, Xiaoyan; Cao, Jinbin; Liu, Wenlong; Ma, Yuduan; Lu, Haoyu; Yang, Junying; Li, L. Y.; Liu, Xu; Wang, Jing; Wang, Tieyan; Yu, Jiahong

doi:10.1002/2014ja020855

Cited by 30 publications

(32 citation statements)

References 36 publications

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“…This result indicates a possible connection to the flow-braking region which is usually found at similar downtail distances (see, e.g. Baumjohann and Glassmeier, 1984, Shiokawa et al, 1997, Dubyagin et al, 2010, and Yao et al, 2012 for observations and possible mechanisms). To study possible hemispheric differences in the Y and Z directions of the tail, the orbit-wise analysis is carried out in the relevant hemispheres.…”

Section: Radial and Hemispheric Dependencesupporting

confidence: 63%

“…Consequently, no shift of the distribution towards lower polytropic indices as reported by previous works can be observed (Baumjohann and Paschmann, 1989;Goertz and Baumjohann, 1991). Instead, if analyzed individually, both active-and quiet-time distributions are similar and cover a wide range of polytropic indices (e.g., Pang et al, 2015). It should be noted that there is a small portion of events (< 1 %) in the ranges γ → 0 and γ → 4.…”

Section: Resultsmentioning

confidence: 50%

“…Earlier studies have already emphasized the necessity to group the data according to magnetospheric activity, usually using the AE index as a proxy (Baumjohann and Paschmann, 1989;Goertz and Baumjohann, 1991;Pang et al, 2015). Therefore, in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Following suggestions of Goertz and Baumjohann (1991) to use only neutral sheet/midnight data they find an average γ = 1.52. Pang et al (2015) use CLUS-TER data of the central plasma and find a wide variety of polytropic indices ranging from 0.1 to 1.8. Active-and quiettime results are very similar.…”

Section: Frühauff Et Al: Average Plasma Sheet Polytropic Index Asmentioning

confidence: 99%

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Average plasma sheet polytropic index as observed by THEMIS

Frühauff¹,

Mieth²,

Glaßmeier³

2017

Ann. Geophys.

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Abstract. Multi-spacecraft data from the years 2008 to 2015 of the THEMIS mission particularly in the near-Earth plasma sheet are used in order to empirically determine the polytropic index in the quiet and active time magnetotail. The results of a number of previous studies in the 1990s can be confirmed. An analysis of the total database, although showing poor correlation, results in an average polytropic index of γ = 1.72. The active time plasma sheet is well correlated with an average γ = 1.49. However, the data scattering suggests that the analysis of the data in total is not adequate. In order to reduce the timescales, individual spacecraft orbits are analyzed, giving a broad distribution of polytropic indices throughout the plasma sheet. The major part of the distribution falls in a range between γ = 0.67 and γ = 2. Our results indicate a variety of thermodynamic processes in the magnetotail and an all-time presence of heat exchange of the plasma. A description of the plasma sheet using an equation of state with a single γ is probably inadequate. This necessitates the application of more sophisticated approaches, such as a parametrization of the heat flux vector in magnetohydrodynamic equations or a superposition of polytropic indices.

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Section: Radial and Hemispheric Dependencesupporting

confidence: 63%

Section: Resultsmentioning

confidence: 50%

Section: Resultsmentioning

confidence: 99%

Section: Frühauff Et Al: Average Plasma Sheet Polytropic Index Asmentioning

confidence: 99%

See 2 more Smart Citations

Average plasma sheet polytropic index as observed by THEMIS

Frühauff¹,

Mieth²,

Glaßmeier³

2017

Ann. Geophys.

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“…Thus, the adiabatic assumption of plasma sheet ions is not appropriate. Pang et al (2015aPang et al ( , 2015b adopted the approach of MHD Bernoulli integral and found that the polytropic index of background plasma sheet ions have a wide distribution around γ~1.0. Pang et al (2015aPang et al ( , 2015b adopted the approach of MHD Bernoulli integral and found that the polytropic index of background plasma sheet ions have a wide distribution around γ~1.0.…”

Section: 1029/2019ja026681mentioning

confidence: 99%

Kinetic Analysis of the Energy Transport of Two‐Flow Components in the Plasma Sheet

Cao

Ren

2019

JGR Space Physics

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Satellite observations indicate that multiple components often exist in the plasma sheet, particularly during impulsive fast flow events. In this paper, we perform a kinetic analysis of the energy transport of plasma sheet ion flow using a model of two‐component plasma sheet ion flows (Background convection flow represented by subscript “b” and Fast flow represented by subscript “f”) and compare the energy transport calculated by kinetic approach Qk with those obtained from magnetohydrodynamic (MHD) approach QMHD. The ratio of Qk/QMHD is always larger than unity and is positively proportional to the ratios of Vf/Vb and Tf/Tb. The maximum values of Qk/QMHD occur in the low‐speed ranges (i.e., small density ratio Nf/N). When Nf/N exceeds 0.4, the ratio of Qk/QMHD is almost the same for a wide parameter ranges of Vf, Tf, and Vb. Heat flux is important in low‐speed range and is neglectable in the high‐speed range. The adiabatic polytropic index 5/3 cannot correctly describe energy transport rate. A density ratio Nf/N of 0.3% of high‐speed ion flow can make the effective polytropic index obviously deviate from adiabatic polytropic index (5/3). The above theoretic results can well explain previously reported satellite in situ observations.

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Polytropic index of magnetosheath ions based on homogeneous MHD Bernoulli Integral

Pang

Cao

2016

JGR Space Physics

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This paper uses Cluster data during the period from 2001 to 2010 to study the polytropic processes of magnetosheath ions. Utilizing the method of homogeneous magnetohydrodynamic (MHD) Bernoulli integral (MBI), we first identify streamflow tubes, then use the constant of polytropic relation to guarantee that the streamflow tube experiences an unchanged polytropic process, and finally determine the polytropic index of ions in these streamflow tubes. The statistical results show that the magnetosheath is a complicated system in which the polytropic index of ions ranges from −2 to 3. The polytropic index distribution of ions is dependent on the electromagnetic energy flux perpendicular to the streamline. The median polytropic index of ions in the magnetosheath is 0.960, 0.965, and 0.974 for perpendicular electromagnetic energy ratio δE × B < 5%, δE × B < 3%, and δE × B < 1%, respectively. There are two basic polytropic processes in the magnetosheath: the dominant isothermal process and the isobaric process. When there is no exchange of electromagnetic energy between neighboring streamflow tubes, the magnetosheath ions are isothermal. However, when the perpendicular electromagnetic energy ratio increases, the isobaric polytropic process starts to emerge. The magnetosheath ion flows are highly localized because most streamflow tubes experiencing same polytropic processes last less than 60 s. Thus, the polytropic index of magnetosheath ion flows is highly variable.

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Polytropic index of central plasma sheet ions based on MHD Bernoulli integral

Cited by 30 publications

References 36 publications

Average plasma sheet polytropic index as observed by THEMIS

Average plasma sheet polytropic index as observed by THEMIS

Kinetic Analysis of the Energy Transport of Two‐Flow Components in the Plasma Sheet

Polytropic index of magnetosheath ions based on homogeneous MHD Bernoulli Integral

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