Polar spots in rapidly rotating stars: stellar wind and evolution of exoplanets

We aim to study large-scale shallow water waves in the tachoclinesof rapidly rotating stars and their connection to the periodicity and the formation of starspotsat high latitudes. Shallow water magnetohydrodynamic equations are used to study the dynamics of largescale waves at the rapidly rotating stellar tachoclinesin the presence of toroidal magnetic field. We found that low frequency magnetic Rossby wavestend to locate at poles, but high frequency magnetic Poincare waves are concentrated near the equator in rapidly rotating stars. Unstable magnetic Rossby wavesmay lead to the local enhancement of magnetic fluxat high latitudes of tachoclinesin rapidly rotating stars. The enhanced magnetic fluxmay rise upwards due to the magnetic buoyancy in the form of tubes and appear as starspotsat polar regions. Magnetic Rossby wavesmay also cause observed short term periodicity in the stellarmagnetic activity. These results have important implications for the evolution of the stellar windand exoplanetsin young Sun-like stars.