TY - JOUR
T1 - Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares
T2 - Connecting Loop-top and Footpoint Hard X-Ray Sources
AU - Kong, Xiangliang
AU - Chen, Bin
AU - Guo, Fan
AU - Shen, Chengcai
AU - Li, Xiaocan
AU - Ye, Jing
AU - Zhao, Lulu
AU - Jiang, Zelong
AU - Yu, Sijie
AU - Chen, Yao
AU - Giacalone, Joe
N1 - Funding Information:
X.K. thanks Drs. Mijie Shi and Shaoxia Chen for valuable discussions on the stochastic differential equations of the focused transport equation. B.C. thanks Lindsay Glesener and Yixian Zhang for helpful discussions on X-ray emission calculation. X.K. is supported by the National Natural Science Foundation of China (NSFC) under grants 11873036, 42074203, and 11790303 (11790300), the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology, and the Young Scholars Program of Shandong University, Weihai. B.C. acknowledges support by NSF grant AST-2108853 to the New Jersey Institute of Technology. F.G. acknowledges support by NSF grant AST-2109154 and from Los Alamos National Laboratory (LANL) through its LDRD program. X.L. acknowledges support by NSF grant AST-2107745. J.Y. acknowledges support by NSFC grant 12073073 and the grant associated with the Applied Basic Research of Yunnan Province 202101AT070018. The work was carried out at National Supercomputer Centers in Guangzhou (TianHe-2) and Tianjin (TH-3F).
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/12/1
Y1 - 2022/12/1
N2 - 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.
AB - 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.
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U2 - 10.3847/2041-8213/aca65c
DO - 10.3847/2041-8213/aca65c
M3 - Article
AN - SCOPUS:85144526523
SN - 2041-8205
VL - 941
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L22
ER -