Chirality of High Latitude Filaments over Solar Cycle 23

TL;DR

This study uses a 15-year simulation to investigate how magnetic helicity transport and differential rotation influence the chirality of high latitude solar filaments throughout Solar Cycle 23.

Contribution

It introduces a long-term simulation model that demonstrates the dominance of helicity transport over differential rotation in determining filament chirality at high latitudes.

Findings

Differential rotation alone can produce opposite chirality at high latitudes for about 5 years after polar field reversal.

Magnetic helicity transport from lower latitudes often overrides differential rotation, maintaining majority chirality.

Long-term helicity transport is crucial for accurate modeling of the solar magnetic field at high latitudes.

Abstract

A non-potential quasi-static evolution model coupling the Sun's photospheric and coronal magnetic fields is applied to the problem of filament chirality at high latitudes. For the first time, we run a continuous 15 year simulation, using bipolar active regions determined from US National Solar Observatory, Kitt Peak magnetograms between 1996 and 2011. Using this simulation, we are able to address the outstanding question of whether magnetic helicity transport from active latitudes can overcome the effect of differential rotation at higher latitudes. Acting alone, differential rotation would produce high latitude filaments with opposite chirality to the majority type in each hemisphere. We find that differential rotation can indeed lead to opposite chirality at high latitudes, but only for around 5 years of the solar cycle following the polar field reversal. At other times, including the rising phase, transport of magnetic helicity from lower latitudes overcomes the effect of in situ differential rotation, producing the majority chirality even on the polar crowns at polar field reversal. These simulation predictions will allow for future testing of the non-potential coronal model. The results indicate the importance of long-term memory and helicity transport from active latitudes when modeling the structure and topology of the coronal magnetic field at higher latitudes.