Numerical Studies of Magnetic Reconnection and Heating Mechanisms for the Ellerman Bomb

刘, 明玉; Ni, Lei; Cheng, Guanchong; Ziegler, Udo; Lin, Jin‐Ming

doi:10.1088/1674-4527/acafc3

Cited by 4 publications

(3 citation statements)

References 60 publications

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“…Two-dimensional particle-incell (PIC) simulations of waves in plasmoid-mediated reconnection have provided new insights into the different natures of waves inside and outside current sheets as an effect of the tearing instability (Shahraki Pour & Hosseinpour 2022). Highresolution 2D MHD simulations with resistivity predicted from particle-collision probabilities including radiative cooling and partially ionised effects have provided detailed information on the energy balance in plasmoid reconnection in the chromosphere leading to EBs (Liu et al 2023) and UV bursts (Ni et al 2022). Though MHD simulations with anomalous resistivity may lead to a slightly more approximate representation of the reconnection process, this study proves that the hyper-diffusion model of Bifrost is indeed helpful in numerically studying phenomena on the Sun that would otherwise require a significantly higher resolution to simulate with a low, Spitzer-like resistivity.…”

Section: Discussionmentioning

confidence: 99%

“…Plasmoids can therefore be expected to be quite numerous in coronal current sheets due to the relatively high Lundquist number. The presence of plasmoids in EBs, UV bursts, surges, and coronal jets has been shown both observationally (e.g., Rouppe van der Voort et al , 2023Kumar et al 2019) and numerically (Ni et al 2017(Ni et al , 2022Nóbrega-Siverio et al 2017;Hansteen et al 2019;Peter et al 2019;Guo et al 2020;Liu et al 2023). Numerical studies of plasmoid-mediated reconnection are therefore key to understanding any reconnection event that may occur in the solar atmosphere.…”

Section: Introductionmentioning

confidence: 96%

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A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

Færder,

Nóbrega-Siverio,

Carlsson

2024

A&A

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Plasmoid-mediated reconnection plays a fundamental role in different solar atmospheric phenomena. Numerical reproduction of this process is therefore essential for developing robust solar models. Our goal is to assess plasmoid-mediated reconnection across various numerical resistivity models in order to investigate how plasmoid numbers and reconnection rates depend on the Lundquist number. We used the Bifrost code to drive magnetic reconnection in a 2D coronal fan-spine topology, carrying out a parametric study of several experiments with different numerical resolution and resistivity models. We employed three anomalous resistivity models: (1) the original hyper-diffusion from Bifrost, (2) a resistivity proportional to current density, and (3) a resistivity quadratically proportional to electron drift velocity. For comparisons, experiments with uniform resistivity were also run. Plasmoid-mediated reconnection is obtained in most of the experiments. With uniform resistivity, increasing the resolution reveals higher plasmoid frequency with weaker scaling to the Lundquist number, obtaining 7.9-12 plasmoids per minute for $S_ L $ with a scaling of $S_ L $ in the highest-resolution resistivity cases, transcending into Petschek reconnection in the high-$S_ L $ limit (where the diffusive effects of the resistivity become small compared to the non-uniform viscosity) and Sweet-Parker reconnection in the low-$S_ L $ limit. Anomalous resistivity leads to similar results even with lower resolution. The drift-velocity-dependent resistivity excellently reproduces Petschek reconnection for any Lundquist number, and similar results are seen with resistivity proportional to current-density though with slightly lower reconnection rates and plasmoid numbers. Among the different resistivity models applied on the given numerical resolution, the hyper-diffusion model reproduced plasmoid characteristics in closest resemblance to those obtained with uniform resistivity at a significantly higher resolution.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

Færder,

Nóbrega-Siverio,

Carlsson

2024

A&A

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“…It is important to point out that several simplifications were made in this study, which is only a rough representation of driven reconnection in the solar atmosphere. For a more detailed study of the reconnection in the Sun, partially ionised effects such as ambipolar diffusion (Zweibel 1989) and the Hall effect (Huang et al 2011) cannot be ignored, especially when studying the energy balance in the chromosphere (Wargnier et al 2023) and the heating mechanisms for EBs (Liu et al 2023) and UV bursts (Ni et al 2022). These effects also play a significant role in the structure of the inflow current density (Snow et al 2018), plasmoid formation (Singh et al 2019;Murtas et al 2021), and reconnection-driven slow-mode shocks (Hillier et al 2016).…”

Section: Discussionmentioning

confidence: 99%

A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

Færder

Nóbrega-Siverio

Carlsson

2023

A&A

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Context. Magnetic reconnection is a fundamental mechanism in astrophysics. A common challenge in mimicking this process numerically in particular for the Sun is that the solar electrical resistivity is small compared to the diffusive effects caused by the discrete nature of codes. Aims. We aim to study different anomalous resistivity models and their respective effects on simulations related to magnetic reconnection in the Sun. Methods. We used the Bifrost code to perform a 2D numerical reconnection experiment in the corona that is driven by converging opposite polarities at the solar surface. This experiment was run with three different commonly used resistivity models: 1) the hyper-diffusion model originally implemented in Bifrost, 2) a resistivity proportional to the current density, and 3) a resistivity proportional to the square of the electron drift velocity. The study was complemented with a 1D experiment of a Harris current sheet with the same resistivity models. Results. The 2D experiment shows that the three resistivity models are capable of producing results in satisfactory agreement with each other in terms of the current sheet length, inflow velocity, and Poynting influx. Even though Petschek-like reconnection occurred with the current density-proportional resistivity while the other two cases mainly followed plasmoid-mediated reconnection, the large-scale evolution of thermodynamical quantities such as temperature and density are quite similar between the three cases. For the 1D experiment, some recalibration of the diffusion parameters is needed to obtain comparable results. Specifically the hyper-diffusion and the drift velocity-dependent resistivity model needed only minor adjustments, while the current density-proportional model needed a rescaling of several orders of magnitude. Conclusions. The Bifrost hyper-diffusion model is as suitable for simulations of magnetic reconnection as other common resistivity models and has the advantage of being applicable to any region in the solar atmosphere without the need for significant recalibration.

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High β magnetic reconnection at different altitudes in the cool low solar atmosphere

Zafar

Lin

et al. 2023

Physics of Plasmas

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We numerically studied magnetic reconnection in a high β hydrogen–helium plasma at different altitudes from the photosphere to the upper chromosphere. The time-dependent ionization degrees were included to get more realistic diffusivities and viscosity, and appropriate radiative cooling models were applied. Our numerical results indicate that the plasmoid instability always plays a vital role in speeding up magnetic reconnection at different atmospheric layers. In addition, both the strong radiative cooling and the magnetic diffusion caused by the electron–neutral collision (ηen) can significantly accelerate magnetic reconnection below the middle chromosphere. On the other hand, both the ambipolar diffusion and the viscosity result in higher temperature and plasma pressure in the reconnection region in the upper chromosphere, which then hinders the fast reconnection process from developing. The local compression heating triggered by turbulent reconnection mediated with plasmoids is the dominant heating mechanism in the unstable reconnection stage at different atmospheric layers, but the viscous heating and the ambipolar diffusion heating are equally important in the upper chromosphere. The Joule heating contributed by ηen dominates during the early quasi-steady reconnection stage below the middle chromosphere, the strong radiative cooling also leads to much stronger compression heating and more generation of thermal energy in this region. Though the plasma β is the same in all the simulation cases at different altitudes, the temperature increase is more significant in the upper chromosphere with much lower density and weaker radiative cooling.

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Numerical Studies of Magnetic Reconnection and Heating Mechanisms for the Ellerman Bomb

Cited by 4 publications

References 60 publications

A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere

High β magnetic reconnection at different altitudes in the cool low solar atmosphere

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