Talk

Do non-dipolar magnetic fields impact spin-down torques?

Victor See, University of Exeter

Low-mass stars with outer convective zones are known to host strong magnetic fields at their surfaces. These fields drive angular momentum- & mass-loss leading to spin-down on the main sequence. One method by which stellar magnetic fields can be characterised is Zeeman-Doppler imaging. This is a powerful technique that can assess the strength and geometry of the large-scale magnetic fields of these stars. This is important because studies have shown that the open flux, which is geometry dependent, is the relevant magnetic property that determines the rate at which stars lose angular momentum. In this talk, I estimate mass-loss rates and spin-down torques for a sample of stars that have been mapped with Zeeman-Doppler imaging. In total, this sample contains over 100 maps. Using the braking law of Finley & Matt (2018), I also determine whether non-dipolar magnetic field modes contribute to the spin-down torque of these stars. For the majority of the stars, only the dipolar field is important. However, there are regimes where the contribution of non-dipolar fields may be non-negligible.