Novel modeling of magneto-rotational stellar evolution
speaker: Koh Takahashi
Abstract
While magnetic fields have been considered to influence the evolution of non-degenerate and compact stars, it has become clear in recent years that actually all stars are deeply affected. We propose a new framework of stellar evolution simulation, in which intertwined evolution between the magnetic fields, the stellar rotation, and the stellar structure is treated self-consistently. In this talk, I will report the results of the magneto-rotational evolution of 1.5 M stars, which have radiatively stratified envelopes during their main-sequence. We have found that the Lorentz force aided by the Omega-effect imposes torsional Alfven waves propagating through the magnetized medium, leading to near-rigid rotation within ~Alfven time. Our results of the hydrogen-burning stage can reproduce the main observed properties of Ap/Bp stars, and moreover, calculations continued to the red-giant regime show a pronounced core-envelope coupling, which reproduces the core and surface rotation periods determined by asteroseismic observations. In addition, I will report on the recent progress of developing a 1D scheme for representing the convective dynamo, which accounts for the magnetic activity of convective stars including the sun. Our new approach reproduces the most fundamental properties of this phenomenon, namely the magnetic field amplification as well as the cyclic behavior.