Our understanding of the structure and dynamics of stellar coronae has
changed dramatically with the availability of surface maps of both star spots
and also magnetic field vectors. Magnetic field extrapolations from these
surface maps reveal surprising coronal structures for stars whose masses and
hence internal structures and dynamo modes may be very different from that of
the Sun. Crucial factors are the fraction of open magnetic flux (which
determines the spin-down rate for the star as it ages) and the location and
plasma density of closed-field regions, which determine the X-ray and radio
emission properties. There has been recent progress in modelling stellar
coronae, in particular the relative contributions of the field detected in the
bright surface regions and the field that may be hidden in the dark star spots.
For the Sun, the relationship between the field in the spots and the large
scale field is well studied over the solar cycle. It appears, however, that
other stars can show a very different relationship.Comment: 6pages, 4 figure
