Analysis on Correlations between Subsurface Kinetic Helicity and Photospheric Current Helicity in Active Regions

TL;DR

This study analyzes the relationship between subsurface kinetic helicity and photospheric current helicity in active regions, revealing a significant correlation that suggests a link between interior dynamics and magnetic twist.

Contribution

It provides the first detailed correlation analysis between subsurface kinetic helicity and photospheric current helicity using vector magnetograms and Doppler data.

Findings

Correlation coefficient above 0.60 between helicities

Phase lag observed in one active region

Indicates intrinsic connection between interior dynamics and magnetic twist

Abstract

An investigation on correlations between photospheric current helicity and subsur- face kinetic helicity is carried out by analyzing vector magnetograms and subsurface velocities for two rapidly developing active regions. The vector magnetograms are from the SDO/HMI (Solar Dynamics Observatory / Helioseismic and Magnetic Im- ager) observed Stokes parameters, and the subsurface velocity is from time-distance data-analysis pipeline using HMI Dopplergrams. Over a span of several days, the evo- lution of the weighted current helicity shows a tendency similar to that of the weighted subsurface kinetic helicity, attaining a correlation coefficient above 0.60 for both ac- tive regions. Additionally, there seems to be a phase lag between the evolutions of the unweighted current and subsurface kinetic helicities for one of the active regions. The good correlation between these two helicities indicate that there is some intrinsic con- nection between the interior dynamics and photospheric magnetic twistedness inside active regions, which may help to interpret the well-known hemispheric preponder- ance of current-helicity distribution.