Stochastic electron acceleration by temperature anisotropy instabilities under solar flare plasma conditions
Author
dc.contributor.author
Riquelme Hernández, Mario Alejandro
Author
dc.contributor.author
Osorio, Alvaro
Author
dc.contributor.author
Verscharen, Daniel
Author
dc.contributor.author
Sironi, Lorenzo
Admission date
dc.date.accessioned
2022-04-25T16:29:16Z
Available date
dc.date.available
2022-04-25T16:29:16Z
Publication date
dc.date.issued
2022
Cita de ítem
dc.identifier.citation
The Astrophysical Journal, 924:52 (13pp), 2022 January 10
es_ES
Identifier
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10.3847/1538-4357/ac3e67
Identifier
dc.identifier.uri
https://repositorio.uchile.cl/handle/2250/185078
Abstract
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Using 2D particle-in-cell plasma simulations, we study electron acceleration by temperature anisotropy instabilities, assuming conditions typical of above-the-loop-top sources in solar flares. We focus on the long-term effect of T ( e,perpendicular to) > T ( e,parallel to) instabilities by driving the anisotropy growth during the entire simulation time through imposing a shearing or a compressing plasma velocity (T ( e,perpendicular to) and T ( e,parallel to) are the temperatures perpendicular and parallel to the magnetic field). This magnetic growth makes T ( e,perpendicular to)/T ( e,parallel to) grow due to electron magnetic moment conservation, and amplifies the ratio omega (ce)/omega (pe) from similar to 0.53 to similar to 2 (omega (ce) and omega (pe) are the electron cyclotron and plasma frequencies, respectively). In the regime omega (ce)/omega (pe) less than or similar to 1.2-1.7, the instability is dominated by oblique, quasi-electrostatic modes, and the acceleration is inefficient. When omega (ce)/omega (pe) has grown to omega (ce)/omega (pe) greater than or similar to 1.2-1.7, electrons are efficiently accelerated by the inelastic scattering provided by unstable parallel, electromagnetic z modes. After omega (ce)/omega (pe) reaches similar to 2, the electron energy spectra show nonthermal tails that differ between the shearing and compressing cases. In the shearing case, the tail resembles a power law of index alpha ( s ) similar to 2.9 plus a high-energy bump reaching similar to 300 keV. In the compressing runs, alpha ( s ) similar to 3.7 with a spectral break above similar to 500 keV. This difference can be explained by the different temperature evolutions in these two types of simulations, suggesting that a critical role is played by the type of anisotropy driving, omega (ce)/omega (pe), and the electron temperature in the efficiency of the acceleration.
es_ES
Patrocinador
dc.description.sponsorship
Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT FONDECYT 1191673
UK Research & Innovation (UKRI)
Science & Technology Facilities Council (STFC) ST/P003826/1
ST/S000240/1
National Science Foundation (NSF) NSF PHY-1748958
Beca EPEC-FCFM
National Laboratory for High Performance Computing (NLHPC) of the Center for Mathematical Modeling of University of Chile ECM-02
es_ES
Lenguage
dc.language.iso
en
es_ES
Publisher
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IOP Publishing
es_ES
Type of license
dc.rights
Attribution-NonCommercial-NoDerivs 3.0 United States