https://doi.org/10.1140/epjp/s13360-024-04946-1
Regular Article
Nonlinear structures in a nonequilibrium plasma: impact of small fluctuations
Plasma Physics Group, Theoretical Physics and Didactic Laboratory, Faculty of Sciences-Physics, University of Bab-Ezzouar (USTHB), Boite Postale 32, El Alia, 16111, Algiers, Algeria
b kam.ourabah@gmail.com, kourabah@usthb.dz
Received:
29
September
2023
Accepted:
28
January
2024
Published online:
19
February
2024
In many plasma environments, e.g., in the solar wind, collisions between particles are rare, challenging therefore the assumption of strict equilibrium. In this paper, we propose to model such nonequilibrium plasmas as a collection of small subsystems that remain infinitely close to equilibrium. This allows us to describe their statistical properties using superstatistics, i.e., a superposition of statistics. Focusing on the three universality classes of superstatistics that have strong empirical evidence (Gamma, inverse-Gamma, and log-normal superstatistics), we study systematically the effect of small thermal fluctuations on the nonlinear structures occurring in plasmas. We focus on the typical scenario of ion acoustic waves in the presence of nonequilibrium electrons and analyze various nonlinear structures governed by the Korteweg–De Vries (KdV) equation and the nonlinear Schrödinger equation. We examine the impact of fluctuations on solitons, rogue waves, and the phenomenon of modulational instability. Our findings demonstrate the universal influence of thermal fluctuations on these structures. Interestingly, the results associated with the Cairns nonthermal distribution, widely addressed in the plasma physics literature, can be recovered by truncating our method to the leading order. Thus, the proposed approach may be regarded as an extension of the Cairns approach, with additional corrections accounting for the different underlying temperature dynamics.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2024. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.