Magnetic flux transport on active cool stars



Rapidly rotating cool stars show signatures of magnetic activity, particularly around their rotational poles, unlike the Sun. We have made numerical simulations that give a possible explanation for the formation of polar spots, besides depicting the effects of large-scale surface flows upon the evolution of starspots. The above figure shows the magnetic field distribution of isolated bipolar magnetic regions when the field strength is about to fall under a detection threshold. Black and yellow show opposite magnetic polarities. White regions covered by black contours indicate regions still above the threshold. Panels a,b): solar-like magnetic regions with an initial tilt with respect to the equator (a) and without tilt (b), 52 days and 45 days after their emergence. c,d): Very large stellar magnetic regions - tilted (c) and non-tilted (d), 218 and 123 days after their emergence. A nonzero tilt angle lead to a longer spot lifetime, particularly for a very large bipolar region (c), which eventually forms a long-living polar cap.

Reference

  • Magnetic flux transport in active cool stars and starspot lifetimes, E. Isik, M. Schüssler, S. K. Solanki, Astron. and Astrophys., 464, 1049-1057 (2007).


    Emre Isik
    Last modified: Sat Apr 12 21:24:37 CEST 2008