On the origin of polytropes in plasmas
Abstract
We present the recent discovery that the polytropic behavior - the specific power-law relationship among the thermal plasma moments- is connected to the statistical framework of kappa distributions. Indeed, the polytropic relationship restricts the functional form of the distribution of particle velocities and energies; surprisingly, the polytropic behavior requires the plasma particles to be described by the framework of kappa distributions. Previously, it was known that kappa distributions can lead to the polytropic relationship. However, the new result shows that the reverse derivation is also true, namely, the polytropic behavior has the role of a mechanism generating kappa distributions. Therefore, the frameworks of polytropes and kappa distributions are equivalent. Ultimately, any observation of a macroscopic polytropic relationship in plasma particle populations constitutes an indirect observation that the microscopic particle velocities and energies are described by kappa distributions. Finally, we show how the derived equivalence between the polytropic behavior and the kappa distribution function can be used in further modeling and data analyses in space plasmas.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH51F3306L
- Keywords:
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- 7827 Kinetic and MHD theory;
- SPACE PLASMA PHYSICS;
- 7829 Kinetic waves and instabilities;
- SPACE PLASMA PHYSICS;
- 7845 Particle acceleration;
- SPACE PLASMA PHYSICS;
- 7863 Turbulence;
- SPACE PLASMA PHYSICS