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

Kong, Xiangliang; Bin, Chen; Guo, Fan; Shen, Chengcai; Li, Xiaocan; Ye, Jing; Zhao, Lulu; Jiang, Zelong; Yu, Sijie; Chen, Yao; Giacalone, J.

doi:10.3847/2041-8213/aca65c

Cited by 13 publications

(7 citation statements)

References 132 publications

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“…In other cases where HXR footpoint sources are co-observed, they are often found to be located at the outer edge of bright EUV flare arcades (e.g., Liu 2013;Krucker & Battaglia 2014). These observations nicely corroborate our scenario: they result from accelerated nonthermal electrons escaping from the ALT magnetic bottle region and reaching the footpoints along the freshly reconnected field lines (see, e.g., recent modeling results by Kong et al 2022a).…”

Section: Discussionsupporting

confidence: 85%

Energetic Electrons Accelerated and Trapped in a Magnetic Bottle above a Solar Flare Arcade

Chen 陈,

Kong,

et al. 2024

ApJ

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Where and how flares efficiently accelerate charged particles remains an unresolved question. Recent studies revealed that a “magnetic bottle” structure, which forms near the bottom of a large-scale reconnection current sheet above the flare arcade, is an excellent candidate for confining and accelerating charged particles. However, further understanding its role requires linking the various observational signatures to the underlying coupled plasma and particle processes. Here we present the first study combining multiwavelength observations with data-informed macroscopic magnetohydrodynamics and particle modeling in a realistic eruptive flare geometry. The presence of an above-the-loop-top magnetic bottle structure is strongly supported by the observations, which feature not only a local minimum of magnetic field strength but also abruptly slowing plasma downflows. It also coincides with a compact above-the-loop-top hard X-ray source and an extended microwave source that bestrides the flare arcade. Spatially resolved spectral analysis suggests that nonthermal electrons are highly concentrated in this region. Our model returns synthetic emission signatures that are well matched to the observations. The results suggest that the energetic electrons are strongly trapped in the magnetic bottle region due to turbulence, with only a small fraction managing to escape. The electrons are primarily accelerated by plasma compression and facilitated by a fast-mode termination shock via the Fermi mechanism. Our results provide concrete support for the magnetic bottle as the primary electron acceleration site in eruptive solar flares. They also offer new insights into understanding the previously reported small population of flare-accelerated electrons entering interplanetary space.

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Section: Discussionsupporting

confidence: 85%

Energetic Electrons Accelerated and Trapped in a Magnetic Bottle above a Solar Flare Arcade

Chen 陈,

Kong,

et al. 2024

ApJ

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“…Flare magnetic reconnection can accelerate electrons in the corona (e.g., Kong et al 2022). These energetic particles produce hard X-ray (HXR) emissions through the bremsstrahlung mechanism.…”

Section: Introductionmentioning

confidence: 99%

The Impulsive Acceleration of a Solar Filament Eruption Associated with a B-class Flare

Wang,

Song,

Chen

et al. 2023

ApJ

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The eruption of magnetic flux ropes (MFRs), often taking filaments together, leads to coronal mass ejections (CMEs). Theoretical studies propose that both the resistive magnetic reconnection and the ideal instability of an MFR system can release magnetic-free energy and accelerate CMEs (i.e., MFRs or filaments) during eruptions. Observations find that the full kinematic evolution of CMEs usually undergoes three phases: the initiation phase, impulsive acceleration phase, and propagation phase. The impulsive acceleration phase often starts and ceases simultaneously with the flare onset time and peak time, respectively. This synchronization can be explained by the positive feedback relationship between the acceleration of CMEs and flare magnetic reconnection, and suggests that the reconnection has the dominant contribution to the acceleration of CMEs. It is rare to see strong evidence that supports the dominant contribution of ideal instability to the acceleration. In this paper, we report an intriguing filament eruption that occurred on 2011 May 11. Its complete acceleration is well recorded by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The kinematic analysis shows that the impulsive acceleration phase starts and ceases obviously earlier than the flare onset time and peak time, respectively, which means a complete asynchronization between the impulsive acceleration phase and flare rise phase, and strongly supports that the ideal instability plays a dominant role in this impulsive acceleration. Furthermore, the accompanied flare is a B-class one, also implying that the contribution of reconnection is negligible in the energy release process.

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“…This cartoon from Masson et al (2013) led to a full MHD simulation in 3D, as reported in Masson et al (2019), invoking a reconnection site remote from the flare reconnection associated with the formation of the loop arcade solar wind, direct connectivity would be possible, but the shock may form initially within closed fields (e.g. Kong et al 2022). In this case, the particles would be trapped effectively in loops.…”

Section: Flare and Cme Modelsmentioning

confidence: 79%

Extreme Solar Events: Setting up a Paradigm

Usoskin,

Miyake,

Baroni

et al. 2023

Space Sci Rev

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The Sun is magnetically active and often produces eruptive events on different energetic and temporal scales. Until recently, the upper limit of such events was unknown and believed to be roughly represented by direct instrumental observations. However, two types of extreme events were discovered recently: extreme solar energetic particle events on the multi-millennial time scale and super-flares on sun-like stars. Both discoveries imply that the Sun might rarely produce events, called extreme solar events (ESE), whose energy could be orders of magnitude greater than anything we have observed during recent decades. During the years following these discoveries, great progress has been achieved in collecting observational evidence, uncovering new events, making statistical analyses, and developing theoretical modelling. The ESE paradigm lives and is being developed. On the other hand, many outstanding questions still remain open and new ones emerge. Here we present an overview of the current state of the art and the forming paradigm of ESE from different points of view: solar physics, stellar–solar projections, cosmogenic-isotope data, modelling, historical data, as well as terrestrial, technological and societal effects of ESEs. Special focus is paid to open questions and further developments. This review is based on the joint work of the International Space Science Institute (ISSI) team #510 (2020–2022).

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

Cited by 13 publications

References 132 publications

Energetic Electrons Accelerated and Trapped in a Magnetic Bottle above a Solar Flare Arcade

Energetic Electrons Accelerated and Trapped in a Magnetic Bottle above a Solar Flare Arcade

The Impulsive Acceleration of a Solar Filament Eruption Associated with a B-class Flare

Extreme Solar Events: Setting up a Paradigm

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