  Low-frequency Alfven-wave turbulence causes ion trajectories to become
chaotic, or "stochastic," when the turbulence amplitude is sufficiently large.
Stochastic orbits enable ions to absorb energy from the turbulence, increasing
the perpendicular ion temperature even when the fluctuation frequencies are too
small for a cyclotron resonance to occur. In this paper, an analytic expression
for the stochastic heating rate is used in conjunction with an observationally
constrained turbulence model to obtain an analytic formula for the
perpendicular ion temperature as a function of heliocentric distance r, ion
mass, and ion charge in coronal holes for values of r between 2 and 15 solar
radii (Rs). The resulting temperature profiles provide a good fit to
observations of protons and OVI ions at 2Rs < r < 3Rs from the Ultraviolet
Coronagraph Spectrometer (UVCS). Stochastic heating also offers a natural
explanation for several detailed features of the UVCS observations, including
the preferential and anisotropic heating of minor ions, the rapid radial
increase in the OVI temperature between 1.6Rs and 1.9Rs, and the abrupt
flattening of the OVI temperature profile as r increases above 1.9Rs.
