Most theoretical solar wind models assume that the random velocities of
the electrons are Maxwellian. However, if there is a significant
population of suprathermal electrons, they could play an important role
in solar wind acceleration (Olbert 1983). This can be investigated
using the combined information provided by the UVCS and the ``in situ"
measurements by studying the ionization state of the solar wind.
The ionization state of the solar wind is ``frozen in" in a region
where the UVCS provides unique and critical plasma diagnostics,
1.3 
r 
10 
(see review by Owocki, 1983). In
this region the UVCS can provide the temperature, density and velocity information
needed for detailed calculations of the ionization state of the
outflowing solar wind plasma, including constraints on the flow velocities of both
the electron/proton plasma and the heavy ions. The flow speed of the heavy ions
may differ from that of the electron/proton plasma. Studies of the effects of
suprathermal electrons on the charge state distribution of elements have
demonstrated that the relative populations of various states of ionization are
very sensitive to the presence of suprathermal electrons (Owocki and Schudder
1983; Bürgi, 1987). Hence, by comparison of the charge distribution
computed for a wind model with the corresponding charge states and
relative abundances
measured in the solar wind at 1 AU by CELIAS, tight constraints can be
placed on the suprathermal electron population.
The densities can be inferred out to 30 
from C1
measurements carried out by LASCO, inferences of coronal temperatures,
and nonthermal velocities can be made inside 3 
. UVCS will
provide temperatures, electron densities, and velocity widths
between 1.3 to 10 
As pointed out by Bürgi
(1987) an additional empirical constraint is provided by the radial
variation of the helum abundance, another parameter which
UVCS can measure (see the observation program on Abundance of
Elements in the Outer Corona).
Coordinated observations between these three instruments will be carried out in different coronal structures, such as coronal holes, and quiet regions. Using measurements from all three instruments, we can impose tighter constraints on solar wind models.
Energy Transport by Suprathermal Electrons
