Non-thermal particle acceleration and power-law tails via relaxation to universal Lynden-Bell equilibria

Collisionless and weakly collisional plasmas often exhibit non-thermal quasi-equilibria. Among these quasi-equilibria, distributions with power-law tails are ubiquitous. It is shown that the statistical-mechanical approach originally suggested by Lynden-Bell (1967) can easily recover such power-law...

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Bibliographic Details
Published inarXiv.org
Main Authors Ewart, Robert J, Nastac, Michael L, Schekochihin, Alexander A
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 03.09.2023
Subjects
Collisional plasmas
Collisionless plasmas
Particle acceleration
Particle energy
Power law
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Summary:Collisionless and weakly collisional plasmas often exhibit non-thermal quasi-equilibria. Among these quasi-equilibria, distributions with power-law tails are ubiquitous. It is shown that the statistical-mechanical approach originally suggested by Lynden-Bell (1967) can easily recover such power-law tails. Moreover, we show that, despite the apparent diversity of Lynden-Bell equilibria, a generic form of the equilibrium distribution at high energies is a `hard' power-law tail \(\propto \varepsilon^{-2}\), where \(\varepsilon\) is the particle energy. The shape of the `core' of the distribution, located at low energies, retains some dependence on the initial condition but it is the tail (or `halo') that contains most of the energy. Thus, a degree of universality exists in collisionless plasmas.
ISSN:2331-8422