Magnetic Helicity Condensation and the Solar Cycle

Abstract

Solar filaments exhibit a global chirality pattern where dextral/sinistral filaments, corresponding to negative/ positive magnetic helicity, are dominant in the northern/southern hemisphere. This pattern is opposite to the sign of magnetic helicity injected by differential rotation along east-west oriented polarity inversion lines, posing a major conundrum for solar physics. A resolution of this problem is offered by the magnetic helicity-condensation model of Antiochos. To investigate the global consequences of helicity condensation for the hemispheric chirality pattern, we apply a temporally and spatially averaged statistical approximation of helicity condensation. Realistic magnetic field configurations in both the rising and declining phases of the solar cycle are simulated. For the helicity-condensation process, we assume convective cells consisting of positive/negative vorticities in the northern/southern hemisphere that inject negative/positive helicity. The magnitude of the vorticity is varied as a free parameter, corresponding to different rates of helicity injection. To reproduce the observed percentages of dominant and minority filament chiralities, we find that a vorticity of magnitude 2.5×10 −6 s −1 is required. This rate, however, is insufficient to produce the observed unimodal profile of chirality with latitude. To achieve this, a vorticity of at least 5×10 −6 s −1 is needed. Our results place a lower limit on the small-scale helicity injection required to dominate differential rotation and reproduce the observed hemispheric pattern. Future studies should aim to establish whether the helicity injection rate due to convective flows and/or flux emergence across all latitudes of the Sun is consistent with our results.

Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections

“…The implication from these studies is that an additional mechanism is needed for injecting helicity into the corona and concentrating it along PILs. The helicity condensation model provides such a mechanism (Mackay et al, 2018).…”

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

“…This model allows us to study the build-up of stress and energy in the magnetic field during the weeks and months prior to the eruption of the stealth event. The global evolutionary model has been originally developed by van Ballegooijen et al (2000) and Mackay & van Ballegooijen (2006a,b) and applied successfully on numerous occasions to simulate the evolution of the coronal magnetic field (Yeates et al 2008b,a;Yeates & Mackay 2009bMackay et al 2014Mackay et al , 2018Yeates et al 2018). b) is taken at the end of CR 2158 after the large AR complex has rotated behind the limb and an eruption occurs close to the southern polar coronal hole.…”

Understanding the Origins of Problem Geomagnetic Storms Associated with “Stealth” Coronal Mass Ejections

“…In particular, MF models are good at generating sheared and twisted field over high-latitude filament channels (e.g. van Ballegooijen 2004;Su et al 2015;Jibben et al 2016;Yardley et al 2019) and also at reproducing the observed hemispheric pattern of filament chirality (Mackay DH, DeVore CR et al 2018;Yardley et al 2021a). Recently, and have performed continuous MF simulations of the global photospheric and coronal magnetic field over 200 days from 1 September 2014 -20 March 2015 for the 2015 solar eclipse.…”