Determination of the polytropic index in the plasma sheet

1989 ◽  
Vol 16 (4) ◽  
pp. 295-298 ◽  
Author(s):  
Wolfgang Baumjohann ◽  
Götz Paschmann
Keyword(s):  
Plasma Sheet ◽  
Polytropic Index

Observational determination of the adiabatic index in the quiet time plasma sheet

1989 ◽  
Vol 16 (6) ◽  
pp. 563-566 ◽  
Author(s):  
C. Y. Huang ◽  
C. K. Goertz ◽  
L. A. Frank ◽  
G. Rostoker
Keyword(s):  
Plasma Sheet ◽  
Adiabatic Index ◽  
Quiet Time

scholarly journals Average plasma sheet polytropic index as observed by THEMIS

2017 ◽  
Vol 35 (2) ◽  
pp. 253-262 ◽  
Author(s):  
Dennis Frühauff ◽  
Johannes Z. D. Mieth ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Plasma Sheet ◽  
Poor Correlation ◽  
Polytropic Index ◽  
Flux Vector ◽  
Broad Distribution ◽  
Active Time ◽  
Heat Flux Vector ◽  
Spacecraft Orbits ◽  
Spacecraft Data ◽  
Thermodynamic Processes

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.

scholarly journals On the Calculation of the Effective Polytropic Index in Space Plasmas

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 997 ◽  
Author(s):  
Georgios Nicolaou ◽  
George Livadiotis ◽  
Robert T. Wicks
Keyword(s):  
Plasma Density ◽  
Plasma Temperature ◽  
Statistical Error ◽  
Space Plasmas ◽  
Polytropic Index ◽  
Plasma Measurement ◽  
Wind Spacecraft ◽  
Index Value ◽  
The Relationship

The polytropic index of space plasmas is typically determined from the relationship between the measured plasma density and temperature. In this study, we quantify the errors in the determination of the polytropic index, due to uncertainty in the analyzed measurements. We model the plasma density and temperature measurements for a certain polytropic index, and then, we apply the standard analysis to derive the polytropic index. We explore the accuracy of the derived polytropic index for a range of uncertainties in the modeled density and temperature and repeat for various polytropic indices. Our analysis shows that the uncertainties in the plasma density introduce a systematic error in the determination of the polytropic index which can lead to artificial isothermal relations, while the uncertainties in the plasma temperature increase the statistical error of the calculated polytropic index value. We analyze Wind spacecraft observations of the solar wind protons and we derive the polytropic index in selected intervals over 2002. The derived polytropic index is affected by the plasma measurement uncertainties, in a similar way as predicted by our model. Finally, we suggest a new data-analysis approach, based on a physical constraint, that reduces the amount of erroneous derivations.

Case study of small scale polytropic index in the central plasma sheet

2015 ◽  
Vol 58 (11) ◽  
pp. 1993-2001 ◽  
Author(s):  
XueXia Pang ◽  
JinBin Cao ◽  
WenLong Liu ◽  
YuDuan Ma ◽  
HaoYu Lu ◽  
...  
Keyword(s):  
Plasma Sheet ◽  
Small Scale ◽  
Polytropic Index ◽  
Central Plasma ◽  
Central Plasma Sheet

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

2015 ◽  
Vol 120 (6) ◽  
pp. 4736-4747 ◽  
Author(s):  
Xuexia Pang ◽  
Jinbin Cao ◽  
Wenlong Liu ◽  
Yuduan Ma ◽  
Haoyu Lu ◽  
...  
Keyword(s):  
Plasma Sheet ◽  
Polytropic Index ◽  
Central Plasma ◽  
Central Plasma Sheet ◽  
Bernoulli Integral
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