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