Authors: Evan Yerger (Space Science Center), Benjamin Chandran (University of New Hampshire), Vincent David (Space Science Center), Romain Meyrand (Space Science Center/University of Otago)

The sub-Alfvenic Solar Wind is highly imbalanced, with the anti-sunward Elsasser species having much more energy than the sunward species. The recently discovered helicity barrier is therefore expected to have a significant effect on the turbulence properties and heating in the Solar Wind. Assuming the helicity barrier is present, we argue that a sufficient condition for cyclotron heating is the presence of parallel wavelengths on proton inertial length scales at the barrier transition scale. We adopt a flux tube model and a set of assumptions for reflection-driven turbulence, which we use, in conjunction with observationally motivated parameters, to predict the turbulent power at these scales. We then use our model to solve for constraints under which we expect cyclotron heating of the fast Solar Wind. Lastly, we explore the implications of our constraints given recent observational results.