Numerical Simulation of Superhalo Electrons Generated by Magnetic Reconnection in the Solar Wind Source Region

Abstract

Superhalo electrons appear to be continuously present in the interplanetary medium, even at very quiet times, with a power-law spectrum at energies above $\sim$2 keV. Here we numerically investigate the generation of superhalo electrons by magnetic reconnection in the solar wind source region, using the MHD and test particle simulations for both single X-line reconnection and multiple X-line reconnection. We find that the direct current electric field, produced in the magnetic reconnection region, can accelerate electrons from an initial thermal energy of T $\sim 10^5$ K up to hundreds of keV. After acceleration, some of the accelerated electrons, together with the nascent solar wind flow driven by the reconnection, propagate upwards along the newly-opened magnetic field lines into the interplanetary space, while the rest move downwards into the lower atmosphere. Similar to the observed superhalo electrons at 1 AU, the flux of the upward-traveling accelerated electrons versus energy displays a power-law distribution at $\sim$ 2 $-$ 100 keV, $f(E)\sim E^{-\delta }$, with a $\delta$ of $\sim$ 1.5 $-$ 2.4. For single (multiple) X-line reconnection, the spectrum becomes harder (softer) as the anomalous resistivity parameter $\alpha$ (uniform resistivity $\eta$) increases. These modeling results suggest that the acceleration in the solar wind source region may contribute to superhalo electrons.

References in corpus (6)

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• Identification of intermittent multi-fractal turbulence in fully kinetic simulations of magnetic reconnection
• Effect of collisions and magnetic convergence on electron acceleration and transport in reconnecting twisted solar flare loops
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Cited by in corpus (5)

• Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares: Connecting Loop-top and Footpoint Hard X-Ray Sources
• Transition-region explosive events produced by plasmoid instability
• Parker Solar Probe Observations of Suprathermal Electron Flux Enhancements Originating from Coronal Hole Boundaries
• Simulation of Quiet-Sun Hard X-rays Related to Solar Wind Superhalo Electrons
• Electron acceleration by turbulent plasmoid reconnection