Giovedì 3 Ottobre 2019, ore 11:00
Osservatorio Astrofisico di Torino, Sala Seminari di Villa Magliola
Stellar magnetic fields: stability and dynamos
Dr. Fabio Del Sordo
Department of Physics, University of Crete
Abstract
The evolution of stellar magnetism is one of the main problems of modern astrophysics, as it affects directly both stellar evolution and their hosted planetary system. I will present some recent studies about the stability evolution of magnetic fields in the interior of radiative stars. In the first part of the seminar I will present results illustrating how a general stellar magnetic field is unstable, but under some conditions can be at least marginally stabilized. In particular, I will present results related to the stability of toroidal fields and the instability associated with them, namely the Tayler instability. These results have direct application to Ap/Bp stars, which are known to host magnetic fields of the order or superior to 300G. In the second part, I will present dynamo simulations modelling the evolved AP star EK Eridani. This is the most slowly rotating active giant star known and it exhibits a very well organized magnetic field whose origin is still debated: it could be either a remnant of field developed in earlier evolutionary stages, or the result of present dynamo action. I will show how the possibility of having dynamo action in EK Eridani depends on internal differential rotation.
