The Magnetic Energy - Helicity Diagram of Solar Active Regions

TL;DR

This study uses a nonlinear force-free method to analyze solar active regions, revealing a strong correlation between magnetic energy and helicity, which are key indicators of potential solar eruptions.

Contribution

It introduces a novel nonlinear force-free approach to simultaneously measure magnetic energy and helicity in active regions, linking these quantities to eruption likelihood.

Findings

Strong correlation between magnetic energy and helicity.

Eruptive regions have higher energy and helicity thresholds.

Helicity levels match those of typical coronal mass ejections.

Abstract

Using a recently proposed nonlinear force-free method designed for single vector magnetograms of solar active regions we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 162 vector magnetograms corresponding to 42 different active regions. We find a statistically robust, monotonic correlation between the free magnetic energy and the relative magnetic helicity in the studied regions. This correlation implies that magnetic helicity, besides free magnetic energy, may be an essential ingredient for major solar eruptions. Eruptive active regions appear well segregated from non-eruptive ones in both free energy and relative helicity with major (at least M-class) flares occurring in active regions with free energy and relative helicity exceeding 4x10^{31} erg and 2x10^{42} Mx^2, respectively. The helicity threshold agrees well with estimates of helicity contents of typical coronal mass ejections.