The polar wind is an ambipolar plasma outflow from the terrestrial
ionosphere at high latitudes. As the ions drift upward along geomagnetic flux
tubes, they move from collision-dominated to collisionless regions. A Monte
Carlo simulation was used to calculate the temperature and Coulomb collision
frequency in the polar wind. The simulation properly accounted for the
divergence of geomagnetic field lines, the gravitational force, the
polarization electric field, and Coulomb collisions. The temperature was found
to increase with altitude and then decreases due to the interplay between
frictional heating due to Coulomb collisions and adiabatic cooling (due to
diverging geomagnetic field). The Coulomb collision frequency was found to
decrease with altitude. As altitude increases, the ions are accelerated by the
upward directed ambipolar electric field and become less coupled with the
background ions. One of the objectives is to study the consequences of a
velocity distribution function with an enhanced high energy tail for the
injected ions. As the number of high energy ions increases in the tail of the
velocity distribution at the injection point (i.e. kappa parameter decreases),
the temperature increases and decreases.
Journal
Title
An-Najah University Journal for Research - Natural Sciences - Volume 18, Issue 1, 2004