The origin of underdense plasma downflows associated with magnetic reconnection in solar flares

Shen, Chengcai; Bin, Chen; Reeves, Katharine K.; Yu, Sijie; Polito, Vanessa; Xie, Xiande

doi:10.1038/s41550-021-01570-2

Cited by 49 publications

(72 citation statements)

References 63 publications

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“…It is worth mentioning that both S = 10 5 and 10 6 runs in this work may significantly underestimate the plasma compression in the flare loop top region. Because of the high density (and plasma β) setting and limitation of computational resources, we can not reveal the clear termination shock and highly turbulent post-shock plasma features as shown in other similar simulations (Kong et al 2019;Shen et al 2018Shen et al , 2022.…”

Section: Discussionmentioning

confidence: 68%

Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10 Solar Flare

Li,

Guo,

Chen

et al. 2022

Preprint

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The X8.2-class limb flare on September 10, 2017 is among the best studied solar flare events owing to its great similarity to the standard flare model and the broad coverage by multiple spacecraft and ground-based observations. These multiwavelength observations indicate that electron acceleration and transport are efficient in the reconnection and flare looptop regions. However, there lacks a comprehensive model for explaining and interpreting the multi-faceted observations. In this work, we model the electron acceleration and transport in the early impulsive phase of this flare. We solve the Parker transport equation that includes the primary acceleration mechanism during magnetic reconnection in the large-scale flare region modeled by MHD simulations. We find that electrons are accelerated up to several MeV and fill a large volume of the reconnection region, similar to the observations shown in microwaves. The electron spatial distribution and spectral shape in the looptop region agree well with those derived from the microwave and hard X-ray emissions before magnetic islands grow large and dominate the acceleration. Future emission modelings using the electron maps will enable direct comparison with microwave and hard X-ray observations. These results shed new light on the electron acceleration and transport in a broad region of solar flares within a data-constrained realistic flare geometry.

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Section: Discussionmentioning

confidence: 68%

Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10 Solar Flare

Li,

Guo,

Chen

et al. 2022

Preprint

Self Cite

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“…The gravity acceleration is calculated by =g e g y ˆ, where = + g g y R 1 0 2 ( ) ☉ , R ☉ denotes the solar radii, and g 0 = 2.7390 × 10 4 cms −2 . We use a widely used optically thin radiation cooling function L T ( ) (see Klimchuk et al 2008;Ye et al 2020;Shen et al 2022). The background heating, = L H n n T i e cor ( ), is supposed to maintain the initial energy balance in the corona and also keep balancing the cooling effect in the bottom chromosphere region (y < 0.2), where T cor is the initial coronal temperature.…”

Section: Numerical Modelmentioning

confidence: 99%

Current-sheet Oscillations Caused by the Kelvin–Helmholtz Instability at the Loop Top of Solar Flares

Wang

Cheng

Ren

et al. 2022

ApJL

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Current sheets (CSs), long stretching structures of magnetic reconnection above solar flare loops, are usually observed to oscillate; their origins, however, are still puzzled at present. Based on a high-resolution 2.5D MHD simulation of magnetic reconnection, we explore the formation mechanism of CS oscillations. We find that large-amplitude transverse waves are excited by the Kelvin–Helmholtz instability at the highly turbulent cusp-shaped region. The perturbations propagate upward along the CS with a phase speed close to local Alfvén speed thus resulting in the CS oscillations we observe. Though the perturbations damp after propagating for a long distance, the CS oscillations are still detectable. In terms of detected CS oscillations, with a combination of differential emission measure techniques, we propose a new method for measuring the magnetic field strength of the CS and its distribution in height.

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“…The gravity acceleration is calculated by g = −gê y , where g = g 0 / (1 + y/R ) 2 , R denotes the solar radii, and g 0 = 2.7390 × 10 4 cm/s 2 . We use a widelyused optically thin radiation cooling function Λ (T ) (see Klimchuk et al 2008;Ye et al 2020;Shen et al 2022). The background heating, H = n i n e Λ (T cor ), is supposed to maintain the initial energy balance in corona and also keep balancing the cooling effect in the bottom chromosphere region (y < 0.2), where T cor is the initial coronal temperature.…”

Section: Numerical Modelmentioning

confidence: 99%

Current-sheet Oscillations Caused by Kelvin-Helmholtz Instability at the Loop Top of Solar Flares

Wang,

Cheng,

Ren

et al. 2022

Preprint

View full text Add to dashboard Cite

Current sheets (CSs), long stretching structures of magnetic reconnection above solar flare loops, are usually observed to oscillate, their origins, however, are still puzzled at present. Based on a high-resolution 2.5-dimensional MHD simulation of magnetic reconnection, we explore the formation mechanism of the CS oscillations. We find that large-amplitude transverse waves are excited by the Kelvin-Helmholtz instability (KHI) at the highly turbulent cusp-shaped region. The perturbations propagate upward along the CS with a phase speed close to local Alfvén speed thus resulting in the CS oscillations we observe. Though the perturbations damp after propagating for a long distance, the CS oscillations are still detectable. In terms of detected CS oscillations, with a combination of differential emission measure technique, we propose a new method for measuring the magnetic field strength of the CSs and its distribution in height.

show abstract

The origin of underdense plasma downflows associated with magnetic reconnection in solar flares

Cited by 49 publications

References 63 publications

Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10 Solar Flare

Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10 Solar Flare

Current-sheet Oscillations Caused by the Kelvin–Helmholtz Instability at the Loop Top of Solar Flares

Current-sheet Oscillations Caused by Kelvin-Helmholtz Instability at the Loop Top of Solar Flares

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