Oscillatory reconnection and resonant response to wave excitation in 2D coronal null points

Engineering notes

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Chinese explanation / 中文解读

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Original abstract

Null points are magnetic field singularities, where the magnetic field strength rapidly drops to zero. In the solar atmosphere, null points are known sites of magnetic reconnection and wave generation and are associated with highly energetic phenomena, such as flares. The aim of this study is to explore the connection between the properties of oscillatory reconnection at null points and the latter's nature as resonant cavities for waves. We perform a set of 2D and 2.5D magnetohydrodynamics simulations of single null points in a stratified solar atmosphere, using the PLUTO code. We perturb each null point through a single propagating pulse and its reflections from the bottom boundary, hitting the null point in an asymmetrical fashion. This leads to both periodic reconnection events and wave refraction around the null point. We find that each null point imposes frequencies on the reconnection matching those of the waves generated from the individual resonant cavity. These frequencies also differ from those excited by the low frequency driver of the reflected waves returning to the null point, the latter lying outside the $95\%$ confidence interval. As such, excited periodic reconnection can be characterised as oscillatory reconnection, i.e. with properties intrinsic to the null points. Finally, the generated waves at the null propagate across the domain, reminiscent of the observed quasi-periodic fast-propagating waves. We provide results showing a direct connection between oscillatory reconnection and the generated high-frequency wavetrains at null points in the solar corona. The propagating waves generated at the resonant cavity, reminiscent of the observed quasi-periodic fast-propagating waves can provide us a diagnostic tool for the reconnection process at the null point and the coronal plasma conditions.

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• Official / arXiv page
• PDF from original source

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