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Numerous attempts to estimate the rate at which low-mass stars lose angularmomentum over their lifetimes exist in the literature. One approach is to usemagnetic maps derived from Zeeman-Doppler imaging (ZDI) in conjunction withso-called "braking laws". The use of ZDI maps has advantages over other methodsbecause it allows information about the magnetic field geometry to beincorporated into the estimate. However, ZDI is known to underestimatephotospheric field strengths due to flux cancellation effects. Recently,Lehmann et al. (2018) conducted synthetic ZDI reconstructions on a set of fluxtransport simulations to help quantify the amount by which ZDI underestimatesthe field strengths of relatively slowly rotating and weak activity solar-likestars. In this paper, we evaluate how underestimated angular momentum-loss rateestimates based on ZDI maps may be. We find that they are relatively accuratefor stars with strong magnetic fields but may be underestimated by a factor ofup to $\sim$10 for stars with weak magnetic fields. Additionally, were-evaluate our previous work that used ZDI maps to study the relativecontributions of different magnetic field modes to angular momentum-loss. Wepreviously found that the dipole component dominates spin-down for mostlow-mass stars. This conclusion still holds true even in light of the work ofLehmann et al. (2018).

How much do underestimated field strengths from Zeeman-Doppler imaging affect spin-down torque estimates?