Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares: Connecting Loop-top and Footpoint Hard X-Ray Sources

Document Type

Article

Publication Date

12-1-2022

Abstract

The acceleration and transport of energetic electrons during solar flares is one of the outstanding topics in solar physics. Recent X-ray and radio imaging and spectroscopy observations have provided diagnostics of the distribution of nonthermal electrons and suggested that, in certain flare events, electrons are primarily accelerated in the loop top and likely experience trapping and/or scattering effects. By combining the focused particle transport equation with magnetohydrodynamic (MHD) simulations of solar flares, we present a macroscopic particle model that naturally incorporates electron acceleration and transport. Our simulation results indicate that physical processes such as turbulent pitch-angle scattering can have important impacts on both electron acceleration in the loop top and transport in the flare loop, and their influences are highly energy-dependent. A spatial-dependent turbulent scattering with enhancement in the loop top can enable both efficient electron acceleration to high energies and transport of abundant electrons to the footpoints. We further generate spatially resolved synthetic hard X-ray (HXR) emission images and spectra, revealing both the loop-top and footpoint HXR sources. Similar to the observations, we show that the footpoint HXR sources are brighter and harder than the loop-top HXR source. We suggest that the macroscopic particle model provides new insights into understanding the connection between the observed loop-top and footpoint nonthermal emission sources by combining the particle model with dynamically evolving MHD simulations of solar flares.

Identifier

85144526523 (Scopus)

Publication Title

Astrophysical Journal Letters

External Full Text Location

https://doi.org/10.3847/2041-8213/aca65c

e-ISSN

20418213

ISSN

20418205

Issue

2

Volume

941

Grant

AST-2108853

Fund Ref

Shandong University

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