Generation Mechanism for Interlinked Flux Tubes on the Magnetopause

Abstract

We use a global magnetohydrodynamics simulation to analyze transient magnetic reconnection processes at the magnetopause. The solar wind conditions have been kept constant, and an interplanetary magnetic field with large duskward BY and southward BZ components has been imposed. Five flux transfer events (FTEs) with clear bipolar magnetic field signatures have been observed. We observed a peculiar structure defined as interlinked flux tubes (IFTs) in the first and fourth FTE, which had very different generation mechanisms. The first FTE originates as an IFTs and remains with this configuration until its final moment. However, the fourth FTE develops as a classical flux rope but changes its 3‐D magnetic configuration to that of IFTs. This work studies the mechanism for generating IFTs. The growth of the resistive tearing instability has been identified as the cause for the first IFTs formation. We believe that the instability has been triggered by the accumulation of interplanetary magnetic field at the subsolar point where the grid resolution is very high. The evidence shows that two new reconnection lines form northward and southward of the subsolar region. The IFTs have been generated with all the classical signatures of a single flux rope. The other IFTs detected in the fourth FTE developed as a result of magnetic reconnection inside its complex and twisted magnetic fields, which leads to a change in the magnetic configuration from a flux rope of twisted magnetic field lines to IFTs.

On the Ubiquity of Magnetic Reconnection Inside Flux Transfer Event‐Like Structures at the Earth's Magnetopause

“…We further discuss the link between a prevailing large IMF B y component in the solar wind and the formation of such structures. Two mechanisms were proposed by Farinas Perez et al (2018) on the basis of simulation and suggest that interlaced flux tubes may form either through resistive tearing instability developing at the subsolar point or through the evolution of a regular FTE into a more complex 3‐D structure. We propose an additional formation mechanism based on the maximum magnetic shear angle model at the magnetopause (Trattner et al, 2007), which can create bifurcated X‐lines at the dayside magnetopause for large IMF B y .…”

“…First, the influence of the IMF B y on the occurrence of interlaced flux tubes was investigated through simulation by Cardoso et al (2013) and more recently by Farinas Perez et al (2018). When imposing a strong B y component on the IMF together with a southward B z , they observed the formation of two “interlinked” flux tubes (called IFT) out of five FTE‐type structures generated in the simulation.…”

“…The interpretation of some FTE‐type phenomena as complex 3‐D structures with interlaced flux tubes was first proposed by Nishida (1989) and Hesse et al (1990). It was studied through simulations (Lee et al, 1993; Otto, 1995; Cardoso et al, 2013; Farinas Perez et al, 2018) and observed in Cluster data (Louarn et al, 2004) prior to MMS.…”

Control of Magnetopause Flux Rope Topology by Non-local Reconnection

“…A common approach in reconnection studies in global MHD simulations is to apply an anomalous resistivity (Komar et al, 2015), and has been found necessary when simulating substorms (Raeder et al, 2001). However, numerous simulations (Raeder, 2006;Cardoso et al, 2013;Perez et al, 2018) have shown that flux ropes can form with numerical resistivity, and anomalous resistivity has no impact on dayside reconnection (Raeder, 2006).…”

“…Other flux tubes were found to be interlinked with field lines of different topology. Perez et al (2018) further reported a study showing a number of flux ropes spontaneously forming under constant solar wind parameters.…”