Chirality and Magnetic Configurations of Solar Filaments

TL;DR

This study analyzes the chirality and magnetic configurations of 571 erupting solar filaments from 2010 to 2015, revealing hemispheric preferences, variations across solar cycle phases, and the dominance of flux rope magnetic structures.

Contribution

It introduces a new filament drainage method for determining filament chirality and provides comprehensive statistical analysis of their magnetic configurations and hemispheric preferences.

Findings

91.6% of erupting filaments follow the hemispheric rule.

Hemispheric preference decreases slightly during solar cycle 24.

89% of filaments are flux rope type with inverse polarity.

Abstract

It has been revealed that the magnetic topology in the solar atmosphere displays hemispheric preference, i.e., negative/positive helicity in the northern/southern hemisphere, respectively. However, the strength of the hemispheric rule and its cyclic variation are controversial. In this paper, we apply a new method based on filament drainage to 571 erupting filaments from 2010 May to 2015 December in order to determine the filament chirality and its hemispheric preference. It is found that $91.6\%$ of our sample of erupting filaments follow the hemispheric rule of helicity sign. It is found that the strength of the hemispheric preference of the quiescent filaments decreases slightly from $\sim$$97\%$ in the rising phase to $\sim$$85\%$ in the declining phase of solar cycle 24, whereas the strength of the intermediate filaments keeps a high value around $96\pm4\%$ all the time. Only the active-region filaments show significant variations. Their strength of the hemispheric rule rises from $\sim$$63\%$ to $\sim$$95\%$ in the rising phase, and keeps a high value $82\pm5\%$ during the declining phase. Furthermore, during a half-year period around the solar maximum, their hemispheric preference totally vanishes. Besides, we also diagnose the magnetic configurations of the filaments based on our indirect method, and found that in our sample of erupting events, $89\%$ are inverse-polarity filaments with a flux rope magnetic configuration, whereas $11\%$ are normal-polarity filaments with a sheared arcade configuration.