# The Effect of Combined Magnetic Geometries on Thermally Driven Winds I: Interaction of Dipolar and Quadrupolar Fields

**Authors:** Adam J. Finley, Sean P. Matt  
**arXiv:** [1707.04078](https://arxiv.org/abs/1707.04078)  
**Date:** 2017-07-13  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/1707.04078v1/

## Key points

- Study by Adam J. Finley and Sean P. Matt on impact of combined magnetic geometries on thermally driven winds in cool stars with outer convective envelopes
- Focus on interaction between dipolar and quadrupolar fields in loss of angular momentum during main sequence
- 50 MHD simulations with mixed field configurations and 10 simulations for each pure geometry conducted
- Findings show broken power law behavior in stellar wind braking torque with combined magnetic geometries
- Torque scaling accurately predicted by considering dipole component alone or total field strength based on quadrupolar scaling
- Dipole component significant in determining angular momentum loss for Solar parameters
- Research provides insights into how mixed magnetic field configurations influence angular momentum loss in main-sequence cool stars

## Summary

In their study, Adam J. Finley and Sean P. Matt investigate the impact of combined magnetic geometries on thermally driven winds in cool stars with outer convective envelopes. These stars exhibit a variety of magnetic field geometries dominated by the lowest order fields such as the dipole, quadrupole, and octupole modes on large scales. The authors focus on the interaction between dipolar and quadrupolar fields, which play a crucial role in the loss of angular momentum from these objects during the main sequence. Through 50 MHD simulations with mixed field configurations and 10 simulations for each pure geometry, Finley and Matt explore how mixed dipolar and quadrupolar fields affect the spin-down torque in slow-rotator regime stars. They find that the stellar wind braking torque in cases with combined magnetic geometries follows a broken power law behavior. Interestingly, they observe that the torque scaling with field strength can be accurately predicted by considering either the dipole component alone or utilizing the total field strength based on quadrupolar scaling. The results of their simulations provide valuable insights into how mixed magnetic field configurations impact angular momentum loss in main-sequence cool stars. Specifically, for Solar parameters, they highlight that the dipole component of the field is particularly significant in determining angular momentum loss. This research contributes to our understanding of how different magnetic field geometries influence stellar wind outflows and ultimately shape the evolution of cool stars throughout their main sequence phase.