MHD Simulations of the Interaction of Small Polarities in Coronal Holes

Coronal holes are extended regions of open magnetic field with densities significantly lower than the typical background corona. Coronal holes rotate quasi-rigidly in contrast to the underlying photosphere whose rotation rate has a strong latitudinal dependence. All proposed explanations of this phenomenon (i.e., that of Wang and Sheeley and that of Fisk and coworkers) require magnetic reconnection to explain coronal hole evolution. However, until recently, observational surveys seeking evidence of such reconnection have been inconclusive. Newer observations made by the Hinode satellite reveal events (jets) throughout coronal holes that are strongly suggestive of reconnection. We have used our MHD model to investigate magnetic reconnection in coronal holes when for small magnetic field polarities of the same sign as they are pushed closer by surface flows. We will discuss the topological aspects of our simulations and the implications for the physics of coronal holes.