Magnetic Helicity from Multipolar Regions on the Solar Surface

TL;DR

This paper demonstrates that the sign of magnetic helicity in the solar corona can be inferred from the surface magnetic pattern of multipolar regions using a geometric pseudoscalar measure.

Contribution

It introduces a novel method to predict coronal magnetic helicity sign from surface magnetic structures in complex multipolar regions.

Findings

Surface magnetic patterns can reveal coronal helicity sign

A pseudoscalar derived from spot positions predicts helicity

Method works well for complex multipolar regions

Abstract

The emergence of dipolar magnetic features on the solar surface is an idealization. Most of the magnetic flux emergence occurs in complex multipolar regions. Here, we show that the surface pattern of magnetic structures alone can reveal the sign of the underlying magnetic helicity in the nearly force-free coronal regions above. The sign of the magnetic helicity can be predicted to good accuracy by considering the three-dimensional position vectors of three spots on the sphere ordered by their relative strengths at the surface and compute from them the skew product. This product, which is a pseudoscalar, is shown to be a good proxy for the sign of the coronal magnetic helicity.