Magnetohydrodynamic (MHD) simulations. II.

This process is often assumed to be governed by the dipolar component of the magnetic field. However, observed magnetic fields can host strong quadrupolar and/or octupolar components, which may influence the resulting spin-down torque on the star.

In Paper I (Finley & Matt 2017ApJ...845...46F), we used the magnetohydrodynamic (MHD) code PLUTO Mignone+ 2007ApJS..170..228M ; Mignone 2009MSAIS..13...67M) to compute steady-state solutions for stellar winds containing a mixture of dipole and quadrupole geometries. We showed the combined winds to be more complex than a simple sum of winds with these individual components. This work follows the same method as Paper I, including the octupole geometry, which not only increases the field complexity but also, more fundamentally, looks for the first time at combining the same symmetry family of fields, with the field polarity of the dipole and octupole geometries reversing over the equator (unlike the symmetric quadrupole).