  Ultraviolet spectroscopy of the extended solar corona is a powerful tool for
measuring the properties of protons, electrons, and heavy ions in the
accelerating solar wind. The large coronal holes that expand up from the north
and south poles at solar minimum are low-density collisionless regions in which
it is possible to detect departures from one-fluid thermal equilibrium. An
accurate characterization of these departures is helpful in identifying the
kinetic processes ultimately responsible for coronal heating. In this paper,
Ultraviolet Coronagraph Spectrometer (UVCS) measurements of the H I Lyman alpha
line are analyzed to constrain values for the solar wind speed, electron
density, electron temperature, proton temperature (parallel and perpendicular
to the magnetic field) and Alfven-wave amplitude. The analysis procedure
involves creating a large randomized ensemble of empirical models, simulating
their Lyman alpha profiles, and building posterior probability distributions
for only the models that agree with the UVCS data. The resulting temperatures
do not exhibit a great deal of radial variation between heliocentric distances
of 1.4 and 4 solar radii. Typical values for the electron, parallel proton, and
perpendicular proton temperatures are 1.2, 1.8, and 1.9 MK, respectively.
Resulting values for the "nonthermal" Alfven wave amplitude show evidence for
weak dissipation, with a total energy-loss rate that agrees well with an
independently derived total heating rate for the protons and electrons. The
moderate Alfven-wave amplitudes appear to resolve some tension in the
literature between competing claims of both higher (undamped) and lower
(heavily damped) values.
