Abstract

Why do massive stars contain such weak magnetic fields?

Jonathan Braithwaite (University of Bonn)

In the ISM from which stars form, magnetic energy is comparable to thermal and kinetic. Once a star has formed, however, the magnetic energy is many orders of magnitude below equipartition with the gravitational, thermal and usually also the rotational energies. I present a natural explanation for this in terms of magnetic helicity conservation during core collapse, while magnetic energy and flux can be destroyed. In addition, I touch on processes such as meridional circulation and their likely influence on what magnetic field is left over from formation.