Quantitative Characterization of Magnetic Flux Rope Properties for Two Solar Eruption Events

TL;DR

This study quantitatively characterizes magnetic flux ropes in two solar eruption events, linking solar observations with in situ data, and highlights the role of magnetic reconnection in CME formation.

Contribution

It introduces a method combining nonlinear force-free field extrapolation and remote sensing to analyze and compare magnetic flux ropes before and during eruptions.

Findings

Identified pre-existing MFR structure in one event.

Estimated magnetic properties of CME-MFRs including flux and twist.

Reconnection flux significantly contributes to CME-MFR formation.

Abstract

In order to bridge the gap between heliospheric and solar observations of coronal mass ejections (CMEs), one of the key steps is to improve the understanding of their corresponding magnetic structures like the magnetic flux ropes (MFRs). But it remains a challenge to confirm the existence of a coherent MFR before or upon the CME eruption on the Sun and to quantitatively characterize the CME-MFR due to the lack of direct magnetic field measurement in the corona. In this study, we investigate the MFR structures, originating from two active regions (ARs), AR 11719 and AR 12158, and estimate their magnetic properties quantitatively. We perform the nonlinear force-free field extrapolations with preprocessed photospheric vector magnetograms. In addition, remote-sensing observations are employed to find indirect evidence of MFRs on the Sun and to analyze the time evolution of magnetic reconnection flux associated with the flare ribbons during the eruption. A coherent "pre-existing" MFR structure prior to the flare eruption is identified quantitatively for one event from the combined analysis of the extrapolation and observation. Then the characteristics of MFRs for two events on the Sun before and during the eruption, forming the CME-MFR, including the axial magnetic flux, field-line twist, and reconnection flux, are estimated and compared with the corresponding in situ modeling results. We find that the magnetic reconnection associated with the accompanying flares for both events injects significant amount of flux into the erupted CME-MFRs.