Synchrotron-driven instabilities in relativistic plasmas of arbitrary opacity

Fuente: arXiv
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Autore principale: Ochs, Ian E.
Natura: Preprint
Pubblicazione: 2024
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author Ochs, Ian E.
author_facet Ochs, Ian E.
contents Recent work has shown that synchrotron emission from relativistic plasmas leads the electron distribution to form an anisotropic ring in momentum space, which can be unstable to both kinetic and hydrodynamic instabilities. Fundamental to these works was the assumption that the plasma was optically thin, allowing all emitted radiation to escape. Here, we examine the behavior of these instabilities as the plasma becomes more optically thick. To do this, we extend a recently-developed Fokker-Planck operator for synchrotron emission and absorption in mildly relativistic plasmas to fully relativistic plasmas. For a given set of plasma parameters, photons emitted by higher-energy electrons tend to be higher frequency, and thus more easily escape the plasma. As a result, the ratio of the photon emission rate (radiative drag) to absorption rate (radiative diffusion) for a given electron is extremely energy-dependent. Given this behavior, we determine the critical parameters that control the opacity, and show how the plasma gradually transitions to become more isotropic and stable at higher opacity.
format Preprint
id arxiv_https___arxiv_org_abs_2407_13106
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Synchrotron-driven instabilities in relativistic plasmas of arbitrary opacity
Ochs, Ian E.
Plasma Physics
High Energy Astrophysical Phenomena
Recent work has shown that synchrotron emission from relativistic plasmas leads the electron distribution to form an anisotropic ring in momentum space, which can be unstable to both kinetic and hydrodynamic instabilities. Fundamental to these works was the assumption that the plasma was optically thin, allowing all emitted radiation to escape. Here, we examine the behavior of these instabilities as the plasma becomes more optically thick. To do this, we extend a recently-developed Fokker-Planck operator for synchrotron emission and absorption in mildly relativistic plasmas to fully relativistic plasmas. For a given set of plasma parameters, photons emitted by higher-energy electrons tend to be higher frequency, and thus more easily escape the plasma. As a result, the ratio of the photon emission rate (radiative drag) to absorption rate (radiative diffusion) for a given electron is extremely energy-dependent. Given this behavior, we determine the critical parameters that control the opacity, and show how the plasma gradually transitions to become more isotropic and stable at higher opacity.
title Synchrotron-driven instabilities in relativistic plasmas of arbitrary opacity
topic Plasma Physics
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2407.13106