ACTIVITY CYCLES IN UX ARIETIS

By analysing long term radio observations of the binary system UX Arie tis, activity cycles have been discovered which are strongly reminisce nt of those present in the Sun. It is well known that the activity cyc le in the Sun is 11 years, while the general magnetic field reverses e very 11 years, returning to its initial configuration after 22 years, namely after two consecutive cycles of activity. Now we have discovere d in UX Arietis an activity cycle of 25.5 days during which the polari zation reverses and returns to its initial value after about two conse cutive cycles of activity. Moreover as the cycle of 11 years of the Su n is modulated with a period of 90-110 years, poorly estimated due to its long term occurence, we found that the 25.5 days activity cycle in UX Arietis is also modulated with a period of 158 days. The solar act ivity cycle is related to the dynamo at work in the sun's interior. Th e fact of having in UX Arietis the same phenomena as in the Sun but at much shorter time scales (i.e. days instead of years) should make pos sible to acquire better statistics in the future and improve our under standing of the dynamo processes.