  Most of the emission coming from the solar corona is confined into closed
magnetic structures in the form of arcs (loops). Very little is known about the
structure of stellar coronae. The magnetic topology, however, can be inferred
by studying the radio emission coming from electrons trapped in the magnetic
loops. Evident morphological changes are produced in fact by stellar rotation.
We have performed 4 VLBA+Effelsberg runs distributed in time so as to cover
well the rotational period of 6.44 days of the active star UX Arietis. We
present here some preliminary results, from those observations.
