Kinetic Models of Fast Solar Wind Driven by Imbalanced Ion Cyclotron Dissipation - What Will Solar Probe See?

In previous work (e.g. Isenberg & Vasquez, ApJ, 731, 88, 2011), we have shown that resonant dissipation of a turbulently maintained power-law spectrum of ion cyclotron waves can produce a reasonable fast solar wind flow. Kinetic modeling of this ion heating in the expanding collisionless coronal hole must also take into account the effects of gravity, charge-separation electric field, mirror force, inertial force in the accelerating plasma, and ponderomotive Alfvén wave pressure. The combined action of all these processes leads to a characteristic evolution of the proton distribution function, some aspects of which may be independent of the actual mechanism for the perpendicular heating. Our previous model used resonant wave intensities that were "balanced" in that we took the power in outward-propagating waves and sunward-propagating waves to be equal. We also were limited by computational considerations to heliocentric radial positions < 6 Rs. Here, we consider imbalanced cases where the outward-propagating intensities of resonant waves are larger than the sunward intensities, as would be expected from reflection models of turbulent evolution in the solar atmosphere. We also extend our computations to beyond the Alfvenic critical point, into the radial range to be explored by Solar Probe Plus. We will present model results for the solar wind speeds and temperatures as functions of heliocentric radius for various ratios of sunward-to-outward wave intensities. We will also show detailed shapes of the proton distribution function and discuss their radial evolution with particular emphasis on the region accessible to the planned Solar Probe Plus mission.