Numerical Simulation of a Fundamental Mechanism of Solar Eruption with Different Magnetic Flux Distributions

TL;DR

This study uses numerical simulations to explore how different magnetic flux distributions in solar active regions influence eruption mechanisms, confirming the robustness of a fundamental eruption trigger related to magnetic reconnection.

Contribution

It demonstrates that the fundamental eruption mechanism is robust across various flux distributions and reveals that stronger PILs lead to larger eruptions due to increased non-potentiality and more efficient reconnection.

Findings

Stronger PILs produce larger eruptions.

The fundamental mechanism is robust across different flux distributions.

Eruption size correlates with magnetic non-potentiality.

Abstract

Solar eruptions are explosive release of coronal magnetic field energy as manifested in solar flares and coronal mass ejection. Observations have shown that the core of eruption-productive regions are often a sheared magnetic arcade, i.e., a single bipolar configuration, and, particularly, the corresponding magnetic polarities at the photosphere are elongated along a strong-gradient polarity inversion line (PIL). It remains unclear what mechanism triggers the eruption in a single bipolar field and why the one with a strong PIL is eruption-productive. Recently, using high accuracy simulations, we have established a fundamental mechanism of solar eruption initiation that a bipolar field as driven by quasi-static shearing motion at the photosphere can form an internal current sheet, and then fast magnetic reconnection triggers and drives the eruption. Here we investigate the behavior of the fundamental mechanism with different photospheric magnetic flux distributions, i.e., magnetograms, by combining theoretical analysis and numerical simulation. Our study shows that the bipolar fields of different magnetograms, as sheared continually, all exhibit similar evolutions from the slow storage to fast release of magnetic energy in accordance with the fundamental mechanism, which demonstrates the robustness of the mechanism. We further found that the magnetograms with stronger PIL produce larger eruptions, and the key reason is that the sheared bipolar fields with stronger PIL can achieve more non-potentiality, and their internal current sheet can form at a lower height and with a larger current density, by which the reconnection can be more efficient. This also provides a viable trigger mechanism for the observed eruptions in active region with strong PIL.