Electric Currents in the Solar Atmosphere: Diagnostics, Properties, and Possible Role in Pre-Eruption Dynamics

Abstract:

The advent of solar vector magnetography, albeit only at photospheric level, typically, has enabled intriguing new capabilities toward the study of solar atmospheric magnetism. A prominent such capability is the evaluation of Ampere’s law in its differential and integral formats. This allows both the calculation of the vertical component of the photospheric electric current density and, notably, the calculation of the total electric current that enters the solar atmosphere via emerging magnetic flux crossing the photospheric interface. We review these diagnostics and the properties of both current density and total current of solar magnetic structures, comparing the results with classical theoretical predictions. The [non]-neutralization of electric currents along magnetic polarity inversion lines is another key issue viewed here under a new perspective, namely the way in which it may be contributing to the triggering of solar eruptions. The results of this analysis have been tailored for solar physics research but apply also to Sun-like, magnetically active stars with a dynamo and a convection zone and, apparently, to every magnetized system in nature that involves a low-beta plasma parameter.