We present test-particle simulations of electrons during a nonlinear magnetohydrodynamic (MHD) simulation of a type-I edge localized mode to explore the effect of an eruptive plasma filament on the kinetic level. The electrons are moderately heated and accelerated during the filamentary eruption on a fast timescale of the order of 0.5 ms. A clearly non-thermal tail is formed in the distribution of the kinetic energy that is of power-law shape and reaches 90 keV for some particles. The acceleration is exclusively observed in the direction parallel to the magnetic field, i.e., with a clear preference in countercurrent direction, and we show that the parallel electric field is the cause of the observed acceleration. Most particles that escape from the system leave at one distinct strike-line in the outer divertor leg at some time during their energization. The escaping high-energy electrons in the tail of the energy distribution are not affected by collisions; thus, they show characteristics of runaway electrons. The mean square displacement indicates that transport in energy space clearly is superdiffusive, and interpreting the acceleration process as a random walk, we find that the distributions of energy-increments exhibit exponential tails, and transport in energy space is equally important of convective (systematic) and diffusive (stochastic) nature. By analyzing the MHD simulations per se, it turns out that the histograms of the parallel electric field in the edge region exhibit power-law shapes, and this clearly non-Gaussian statistics is ultimately one of the reasons for the moderately anomalous phenomena of particle transport that we find in energy space.
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November 2022
Research Article|
November 09 2022
Filamentary plasma eruptions and the heating and acceleration of electrons
Heinz Isliker
;
Heinz Isliker
a)
(Conceptualization, Data curation, Investigation, Methodology, Software, Visualization, Writing – original draft, Writing – review & editing)
1
Astronomy Laboratory, Department of Physics, Aristotle University of Thessaloniki
, 541 24 Thessaloniki, Greece
a)Author to whom correspondence should be addressed: [email protected]
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Andres Cathey
;
Andres Cathey
(Data curation, Software, Visualization, Writing – original draft, Writing – review & editing)
2
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching bei München, Germany
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Matthias Hoelzl
;
Matthias Hoelzl
(Conceptualization, Data curation, Software, Writing – original draft, Writing – review & editing)
2
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching bei München, Germany
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Stanislas Pamela
;
Stanislas Pamela
(Conceptualization, Data curation, Software, Writing – original draft)
3
CCFE, Culham Science Centre
, Abingdon OX14 3DB, United Kingdom
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Loukas Vlahos
Loukas Vlahos
(Conceptualization, Writing – original draft, Writing – review & editing)
1
Astronomy Laboratory, Department of Physics, Aristotle University of Thessaloniki
, 541 24 Thessaloniki, Greece
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a)Author to whom correspondence should be addressed: [email protected]
Phys. Plasmas 29, 112306 (2022)
Article history
Received:
July 27 2022
Accepted:
October 18 2022
Citation
Heinz Isliker, Andres Cathey, Matthias Hoelzl, Stanislas Pamela, Loukas Vlahos; Filamentary plasma eruptions and the heating and acceleration of electrons. Phys. Plasmas 1 November 2022; 29 (11): 112306. https://doi.org/10.1063/5.0115754
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