Poster Abstracts

Name/Affiliation:  Gordon Gibb (University of St Andrews)

Title:  Investigating the Coronal Dynamics of High Differential Rotation Stars

We investigate the effects of various differential rotation rates and photospheric surface diffusion constants on the formation time and lifetime of a flux rope formed along the polarity inversion line of a decaying bipolar active region. In order to do this we apply a magnetic flux transport model to determine the evolution of the stellar photospheric field. This evolving photospheric field is used to drive the evolution of the coronal magnetic via a magnetofrictional technique. We find that increasing the differential rotation rates (decreasing equator-pole lap times) decreases the flux rope formation times. Increasing the photospheric surface diffusion decreases the formation times. We find that the formation time is approximately proportional to the square root of the lap time. The lifetimes of flux ropes are found to be proportional to the lap times, with stars with differential rotation rates of eight days having lifetimes of only two days. We conclude that such high differential rotation stars may have very dynamical coronae. Additionally, we propose that features such as the prominences observed on the Sun may not be able to form on very high differential rotation stars, as the lifetimes of the flux ropes in which the cool plasma condenses may be shorter than the radiative collapse timescale for the plasma.