Analysis of the effect of turbulent diffusion in the solar flare current sheet

(ORDO NEWS) — Researchers from the Yunnan Observatories of the Chinese Academy of Sciences studied the turbulent properties in the large-scale current sheet (CS) of a solar flare.

They quantified the rate of magnetic reconnection, diffusion, scale of dissipation, amplitude of turbulence, and so on.

After the appearance of turbulence caused by discontinuous instabilities. They found that turbulence can effectively increase the width of the CS and introduce an additional dissipation effect into the CS.

A solar flare is one of the most energetic events in the solar system, releasing up to 1032 ergs of magnetic energy. This large-scale current sheet, connecting with the flare and erupting flow, is the main site for the magnetic reconnection process.

Classical theories predict an ionic inertia scale width of TC of tens or hundreds of meters, while many observations have found a corresponding width of 104 to 105 km.

The huge discrepancy may be due to the turbulence that occurs in the vehicle. Thus, an accurate estimate of the energy dissipation caused by turbulence is critical to understanding the rapid energy release in a solar flare.

In this study, the scientists used high-resolution 2D magnetohydrodynamic numerical models based on a standard flare model in a gravitationally stratified solar atmosphere. The rate of magnetic reconnection showed an obvious increase due to the appearance of discontinuous instabilities.

They found that the appearance of turbulence is equivalent to adding an additional dissipative term to the induction equations, which can dramatically increase local diffusion in the CS.

“According to the spectral analysis, we calculated an associated dissipation scale of 100-200 km, which was much higher than the ion-inertial scale.

This corresponded to the width of the secondary reconnection of the TC between the merging plasmoids,” said Zhang Yining, first author of the study.

In addition, they calculated the total width of the current sheet as 1500-2500 km, which is consistent with the observational results. Indeed, the width of the CS, which is often encountered in observations, turns out to correspond to the Taylor scale from Biskamp’s theory.

“The shock wave at the top of the plume loop can slightly increase the amplitude of turbulence. The amplification factor is related to the local geometry of the shock wave, and it is shown that the shock wave has a higher heating efficiency than the transfer of kinetic energy,” said Dr. Ye Jing, corresponding author of the study.

This study elucidates the details of the mechanism of magnetic reconnection dissipation in the presence of turbulence in a solar flare.

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