
%0 Journal Article
%A Wheatland, MS 
%A Melrose, DB 
%T Cross-field Current Closure Below the Solar Photosphere
%J Australian Journal of Physics
%D 1994/06/01
%V 47
%N 3
%P 361-374
%K 
%R https://doi.org/10.1071/PH940361
%U https://www.publish.csiro.au/paper/PH940361 
%X A simple model is developed to describe how an externally imposed current closes as a function of time below the photosphere. A vertical current density is assumed to turn on at the photospheric boundary. The model implies that the subsequent closure of the current in the sub-photosphere depends only on the ratio RA/ R, where RA = /-LaVA is the Alfvenic impedance of the photosphere and = I/o-pI is the resistance corresponding to the conductivity O-p and a characteristic length 1. For RA/R » 1, current closure occurs at a front, propagating with the Alfven speed. For RA/ R 1, current closure is a diffusive process ahead and behind a slowly propagating Alfvenic front. The first case is the relevant one for the Sun, where RA/ R /VA, for VA in kilometres per second. 
