# A Study of Pre-flare Solar Coronal Magnetic Fields: Magnetic Energy and Helicity

## TL;DR

This study analyzes pre-flare solar coronal magnetic fields to identify parameters that distinguish eruptive from confined flares, finding that certain normalized indices effectively predict flare types with over 75% accuracy.

## Contribution

It introduces and evaluates specific magnetic energy and helicity ratios as predictors for flare eruptiveness, demonstrating their effectiveness in distinguishing flare types.

## Key findings

- Normalized energy and helicity ratios effectively differentiate eruptive and confined flares.
- Eruptive flares have higher average non-potentiality and complexity in magnetic fields.
- Critical thresholds of $E_F/E_P$ and $|H_J/\

## Abstract

Solar flares fall into two types with eruptive ones associated with coronal mass ejection (CME) and confined ones without CME. To explore whether there are pre-flare conditions in terms of magnetic energy and helicity that can effectively determine the types of flares, here we analyzed a suite of related parameters of the reconstructed pre-flare coronal magnetic field of major solar flares, either eruptive or confined, from 2011 to 2017 near the solar disk center. The investigated parameters include the extensive-type quantities such as the total magnetic energy $E_T$, the potential energy $E_P$, the free energy $E_F$, the relative helicity $H_R$, and the non-potential helicity $H_J$, as well as the intensive-type indices $E_F/E_P$, $|H_J/H_R|$, $|H_R/\phi^{\prime2}|$ and $|H_J/\phi^{\prime2}|$, where $\phi^{\prime}$ is half of the total unsigned magnetic flux. We have the following key findings: (1) None of the extensive parameters can effectively distinguish the eruptive and confined potential of the pre-flare coronal fields, though the confined events have averagely larger values; (2) All the intensive parameters have significantly larger average and median values for eruptive flares than the confined events, which indicates that the field for eruptive flares have overall higher degree of non-potentiality and complexity than that of the confined flares; (3) The energy ratio $E_F/E_P$ and the normalized non-potential helicity $|H_J/\phi^{\prime2}|$, which are strongly correlated with each other, have among the highest capability of distinguishing the fields that possibly produce a major eruptive or confined flare, as over 75\% of all the events are successfully discriminated between eruptive and confined flares by using critical values of $E_F/E_P\ge0.27$ and $|H_J/\phi^{\prime2}|\ge0.009$.