Physics

Prof Dinshaw Balsara
Notre Dame University, USA,

                In this talk, I present the first set of 3D magnetohydrodynamic (MHD) simulations performed with the Riemann-Geomesh code. We study the dynamics of the magnetically channeled winds of magnetic massive stars in full 3D using a code that is uniquely suited to spherical problems. Specifically, we perform isothermal simulations of a smooth wind on a rotating star with a tilted, initially dipolar field. We compare the mass-loss, angular momentum loss, and magnetospheric dynamics of a template star (with the properties that are reminiscent of the O4 supergiant ζ-Pup) over a range of rotation rates, magnetic field strengths, and magnetic tilt angles. The simulations are run up to a quasi-steady state, showing the episodic centrifugal breakout events of the mass outflow, confined by the magnetic field loops that form the closed magnetosphere of the star. The catalogued results provide perspective on how angular momentum varies for different configurations of rotation rate, magnetic field strength and large magnetic tilt angles. In agreement with previous 2D MHD studies, we find that high magnetic confinement reduces the overall mass-loss rate, and higher rotation increases the mass-loss rate. In addition, we estimate the angular-momentum evolution, spin-down time, and mass-loss evolution of magnetic massive stars for different values of magnetic field strength, rotation rate, and dipole tilt.