The global magnetic topology of AB Doradus

摘要: We have used Zeeman-Doppler maps of the surface field young, rapid rotator AB Dor (P r o t = 0.514 d) to extrapolate coronal field, assuming it be potential. find that topology large-scale is very similar in all three years for which we images. The corona divides cleanly into regions open and closed field. originates two mid-latitude opposite polarity separated by about 180° longitude. region forms a torus extending almost over each pole, with an axis runs through these longitudes. investigated effect on global different flux unobservable hemisphere dark polar spot where Zeeman signal suppressed. distribution affects only low-latitude topology, whereas imposition unidirectional forces cap open. This contradicts observations suggest extends high latitudes leads us propose may composed multipolar regions.