Peter Wyper (Durham): MHD simulations of Coronal Hole Bright Points and Jets
The low corona within coronal holes is dotted with bright points of different shapes, sizes and durations when viewed in X-rays or EUV. Some are transient, lasting a few minutes, and are associated with coronal jets. Others are much longer lived, lasting a few hours, and have periodic variations in intensity. These long-lived bright points sometimes produce jets, but not always. Magnetograms show that beneath most long-lived bright points there are two interacting magnetic polarities of opposite sign. It is generally believed that reconnection driven by the interaction of the polarities is what heats the plasma in the connecting loops, producing the observed bright point. However, the details of how and where this reconnection occurs are still under debate.
Magnetic fragments form or interact on the solar photosphere via three main mechanisms: flux emergence, relative motion or cancellation. In this talk I will discuss a series of simulations which focus on the relative motion aspect, starting with a uniformly advected isolated minority polarity and progressing to a “fly-by” of a minority and majority polarity feature. I will show how these simple evolutions can produce many of the features of long-lived coronal hole bright points, including their long-duration periodic intensity variations and their occasional launching of jets.