THE EFFECT OF WAVE-PARTICLE INTERACTIONS ON THE POLAR WIND O+

The escape of the polar wind plasma is an important element in the ionosphere-magnetosphere coupling. Both theory and observations indicate that the wave-particle interactions (WPI) play a significant role in the dynamics of ion outflow along open geomagnetic field lines. A Monte Carlo simulation was developed in order to include the effect of the WPI in addition to the factors that are traditionally included in the 'classical' polar wind (i.e. gravity, electrostatic field, and divergence of geomagnetic field lines). The ion distribution function (f(j)), as well as the profiles of its moments (density, drift velocity, temperature, etc.) were found for different levels of WPI, that is, for different values of the normalized diffusion rate in the velocity space (D(perpendicular-to j)). Although the model included O+, H+ and electrons, we presented only the results related to the O+ ion. We found that (1) both the density and drift velocity of O+ increased with the WPI strength, and consequently, the O+ escape flux was enhanced by a factor of up to 10(5); (2) The O+ ions could be energized up to a few electron volts; (3) for moderate and high levels of WPI (D(perpendicular-to)(O+) > 1), the distribution function f(O+) displayed very pronounced conic features at altitudes around 3R(e). Finally, the interplay between the downward body force, the upward mirror force, and the perpendicular heating resulted in the formation of the ''pressure cooker'' effect. This phenomena explained some interesting features of our solution, such as, the peak in the O+ temperature, and the formation of ''ears'' and conics for f(O+) around 2.5R(e).