Stellar X-ray emission as an indicator of stellar magnetic activity

The role of recent Einstein Observatory observations and theoretical models of stellar X-ray emission in furthering current understanding of stellar magnetic activity is discussed. It is suggested that solar observations can be used to show that coronal emission is morphologically related to surface magnetic field activity, as well as to establish a quantitative link between observed soft X-ray flux and the mean surface magnetic flux. It is demonstrated that soft X-ray emission is a sensitive diagnostic for the presence of surface magnetic fields, since it is unaffected by radiative transfer effects and the resulting coupling to the underlying atmosphere. Stellar coronal emissions are therefore an excellent probe for the study of stellar magnetic activity over a wide dynamic range.