The origin and effect of hemispheric helicity imbalance in solar dynamo

Abstract

In this paper we study the effects of the net magnetic helicity density on the hemispheric symmetry of the dynamo generated large-scale magnetic field. Our study employs the axisymmetric dynamo model which takes into account the nonlinear effect of magnetic helicity conservation. We find that, on the surface, the net magnetic helicity follows the evolution of the parity of the large-scale magnetic field. Random fluctuations of the $\unicode[STIX]{x1D6FC}$ -effect and the helicity fluxes can invert the causal relationship, i.e. the net magnetic helicity or the imbalance of magnetic helicity fluxes can drive the magnetic parity breaking. We also found that evolution of the net magnetic helicity of the small-scale fields follows the evolution of the net magnetic helicity of the large-scale fields with some time lag. We interpret this as an effect of the difference of the magnetic helicity fluxes out of the Sun from the large and small scales.

A study of global magnetic helicity in self-consistent spherical dynamos

“…More work is needed to develop this area, but the interpretation of helicity in terms of toroidal/poloidal linkage may help to develop existing mean-field models which attempt to explain hemisphere imbalances (e.g. Yang et al, 2020).…”

Hemispheric Distribution of Halo Coronal Mass Ejection Source Locations

“…Ribes & Nesme-Ribes (1993) discovered that nearly all sunspots observed were in the southern hemisphere and almost none in the northern hemisphere during the Maunder minimum (1645Maunder minimum ( -1715. Other solar activity features are also distributed differently in the northern and southern hemispheres, such as the solar magnetic field (Knaack et al 2004), the flare index (Atacc & Özgücc 1996;Joshi et al 2015), prominences (Verma 2000), polar faculae (Sheeley 2008;Deng et al 2016a), the solar polar magnetic fields (Svalgaard & Kamide 2013;Petrie 2022), the chirality of filaments (Ouyang et al 2017), magnetic helicity (Zhang & Yang 2013;Yang et al 2020), CMEs (Gao et al 2009), the large-scale magnetic field (Obridko et al 2023), and the solar rotation (Li et al 2020;Wan et al 2023). Accordingly, the hemispheric asymmetry of solar activity is a real physical phenomenon (Carbonell et al 1993;Verma 1993;Atacc & Özgücc 1996;Knaack et al 2004;Temmer et al 2006;Badalyan & Obridko 2011;Schüssler & Cameron 2018;Veronig et al 2021).…”