Numerical Simulation of Helical Jets at Active Region Peripheries

TL;DR

This paper presents a 3D magnetohydrodynamic simulation of helical jets at active region edges, revealing the mechanisms behind their formation and comparing results with observations, advancing understanding of solar coronal jets.

Contribution

It introduces a detailed simulation of active-region-periphery jets, highlighting the coupling of breakout reconnection and flux rope instability as their core mechanism.

Findings

Null point replaces bald patch early in eruption

Eruption results from magnetic breakout and kink instability

Simulation results agree with observed jet properties

Abstract

Coronal jets are observed above minority polarity intrusions throughout the solar corona. Some of the most energetic occur on the periphery of active regions where the magnetic field is strongly inclined. These jets exhibit a non-radial propagation in the low corona as they follow the inclined field, and often have a broad, helical shape. We present a three-dimensional magnetohydrodynamic simulation of such an active-region-periphery helical jet. We consider an initially potential field with a bipolar flux distribution embedded in a highly inclined magnetic field, representative of the field nearby an active region. The flux of the minority polarity sits below a bald-patch separatrix initially. Surface motions are used to inject free energy into the closed field beneath the separatrix, forming a sigmoidal flux rope which eventually erupts producing a helical jet. We find that a null point replaces the bald patch early in the evolution and that the eruption results from a combination of magnetic breakout and an ideal kinking of the erupting flux rope. We discuss how the two mechanisms are coupled, and compare our results with previous simulations of coronal-hole jets. This comparison supports the hypothesis that the generic mechanism for all coronal jets is a coupling between breakout reconnection and an ideal instability. We further show that our results are in good qualitative and quantitative agreement with observations of active-region periphery jets.