Formation and dynamics of a solar eruptive flux tube

Satoshi Inoue,Kanya Kusano,Jan Skála,Jörg Büchner

doi:10.1038/s41467-017-02616-8

Satoshi Inoue, Kanya Kusano + Show 2 more

Open Access

https://doi.org/10.1038/s41467-017-02616-8

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Abstract

Solar eruptions are well-known drivers of extreme space weather, which can greatly disturb the Earth’s magnetosphere and ionosphere. The triggering process and initial dynamics of these eruptions are still an area of intense study. Here we perform a magnetohydrodynamic simulation taking into account the observed photospheric magnetic field to reveal the dynamics of a solar eruption in a real magnetic environment. In our simulation, we confirmed that tether-cutting reconnection occurring locally above the polarity inversion line creates a twisted flux tube, which is lifted into a toroidal unstable area where it loses equilibrium, destroying the force-free state, and driving the eruption. Consequently, a more highly twisted flux tube is built up during this initial phase, which can be further accelerated even when it returns to a stable area. We suggest that a nonlinear positive feedback process between the flux tube evolution and reconnection is the key to ensure this extra acceleration.

Highlights

Solar eruptions are well-known drivers of extreme space weather, which can greatly disturb the Earth’s magnetosphere and ionosphere
In order to clarify the dynamics of solar eruptive flux tube in that situation, here we perform the MHD simulation using the photospheric magnetic field from which the initial condition is reconstructed in the nonlinear-force-free field (NLFFF) approximation[20,21]
The 3D magnetic field lines approximated with the NLFFF are displayed in Fig. 3b, which are extrapolated from the photospheric magnetic field

Summary

Introduction

Solar eruptions are well-known drivers of extreme space weather, which can greatly disturb the Earth’s magnetosphere and ionosphere. Recent observations[18,19] confirmed several eruptions occurred even though the decay index takes the saddle-like profile where the flux tube starts launching in an area (n ≥ 1.5), but later returns into TI-stable area (n ≤ 1.5). In order to clarify the dynamics of solar eruptive flux tube in that situation, here we perform the MHD simulation using the photospheric magnetic field from which the initial condition is reconstructed in the nonlinear-force-free field (NLFFF) approximation[20,21]. This was done to shorten the distance between theoretical models and observations, and construct a more realistic magnetic environment. We present detailed analysis of this eruptive flux tube in following section

Methods

Results

Conclusion