Two-fluid simulations of coalescing penumbra filaments driven by neutral-hydrogen flows

Abstract

We study the coalescence of two penumbra filaments driven by neutral-hydrogen flows. We investigate the effects of changing the initial collision velocity and axial current intensity on the magnetic reconnection rates. We use a two-fluid (ion-neutral) numerical code to model the three-dimensional dynamics of protons and neutral-hydrogen particles, which couple through proton/neutral-hydrogen collisions. It is found that the magnetic reconnection rate of the coalescing penumbral filaments is strongly enhanced by an initial collision velocity. An initial collision velocity corresponding to 10% of the sound speed increases the magnetic reconnection rate by a factor of 50 when compared to spontaneous coalescence. We conclude that the magnetic reconnection rate of coalescing penumbra filaments can be strongly enhanced by weak photospheric neutral-hydrogen flows. © 2009. The American Astronomical Society. All rights reserved.