Electron acceleration and small‐scale coherent structure formation by an Alfvén wave propagating in coronal interplume region

Daiffallah, K.; Mottez, Fabrice

doi:10.1002/asna.201713364

Cited by 2 publications

(1 citation statement)

References 58 publications

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“…Phase mixing has been associated with density depletion or cavity (plasma under-density) in auroral regions (Génot et al 1999(Génot et al , 2000Mottez & Génot 2011) or more recently in interplume regions (Daiffallah & Mottez 2017). This mechanism has been associated also with the density bump or plasma over-density in solar coronal loops (Tsiklauri 2007(Tsiklauri , 2011(Tsiklauri , 2012(Tsiklauri , 2016 or in a solar coronal holes (Wu & Fang 2003).…”

Section: Phase Mixing and Longitudinal Density Gradientmentioning

confidence: 99%

Electron acceleration from the interaction of three crossed parallel Alfvén waves

Daiffallah

2022

J. Plasma Phys.

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We study the nonlinear interaction of three parallel Alfvén wave packets (AWPs) in an initially uniform plasma using 2.5-dimensional particle-in-cell (PIC) numerical simulations. We aim to help to explain the observation of suprathermal electrons by the collision of multiple Alfvén waves in regions where these waves are trapped like the IAR (Ionospheric Alfvén Resonator), Earth radiation belts or coronal magnetic loops. In the context of the acceleration by the parallel Alfvén waves interactions (APAWI) process that has been described by Mottez (Ann. Geophys., vol. 30, issue 1, 2012, pp. 81–95; J. Plasma Phys., vol. 81, issue 1, 2015, p. 325810104), the interaction of two parallel Alfvén waves (AWs) generates longitudinal density modulations and parallel electric fields at the APAWI crossing region that can accelerate particles effectively in the direction of the background magnetic field. Our simulations show that when a third parallel AWP of different initial position arrives at the APAWI crossing region, it gives rise to a strong parallel electron beam ( $V \sim 5\text {--}7 V_{Te}$ ) at longitudinal cavity density gradients. We suggest that velocity drift from an outgoing AW generates interface waves in the transverse direction, which allows propagating waves to develop parallel electric fields by the phase mixing process when $k_{\perp }^{-1}$ of the wavy density gradient (oblique gradient) is in the range of the electron inertial length $c/\omega _{p0}$ .

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Section: Phase Mixing and Longitudinal Density Gradientmentioning

confidence: 99%

Electron acceleration from the interaction of three crossed parallel Alfvén waves

Daiffallah

2022

J. Plasma Phys.

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Particle acceleration by sub-proton cyclotron frequency spectrum of dispersive Alfven waves in inhomogeneous solar coronal plasmas

Tsiklauri

2023

Monthly Notices of the Royal Astronomical Society

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The problem of explaining observed soft X-ray fluxes during solar flares, which invokes acceleration of large fraction of electrons, if the acceleration takes places at the solar coronal loop-top, can potentially be solved by postulating that flare at loop-top creates dispersive Alfven waves (DAWs) which propagate towards the foot-points. As DAWs move in progressively denser parts of the loop (due to gravitational stratification) the large fraction of electrons is no longer needed. Here we extend our previous results by considering f−1 frequency spectrum of DAWs and add He++ ions using fully kinetic particle-in-cell (PIC) simulations. We consider cases when transverse density gradient is in the range 4 − 40c/ωpe and DAW driving frequency is 0.3 − 0.6ωcp. We find that (i) The frequency spectrum case does not affect electron acceleration fraction in the like-to-like cases, but few times larger percentage of He++ heating is seen due to ion cyclotron resonance; (ii) In cases when counter propagating DAWs collide multiple-times, much larger electron and ion acceleration fractions are found, but the process is intermittent in time. This is because intensive heating (temperature increase) makes the-above-thermal-fraction smaller; Also more isotropic velocity distributions are seen; (iii) Development of kink oscillations occurs when DAWs collide; (iv) Scaling of the magnetic fluctuations power spectrum steepening in the higher-density regions is seen, due to wave refraction. Our PIC runs produce much steeper slopes than the orginal spectrum, indicating that the electron-scale physics has a notable effect of DAW spectrum evolution.

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Electron acceleration and small‐scale coherent structure formation by an Alfvén wave propagating in coronal interplume region

Cited by 2 publications

References 58 publications

Electron acceleration from the interaction of three crossed parallel Alfvén waves

Electron acceleration from the interaction of three crossed parallel Alfvén waves

Particle acceleration by sub-proton cyclotron frequency spectrum of dispersive Alfven waves in inhomogeneous solar coronal plasmas

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