No abstract

Anomalous electron heat fluxes and recent observations of day‐night asymmetries in polar wind features indicate that photoelectrons may affect polar wind dynamics. These anomalous fluxes require a global kinetic description (i.e., mesoscale particle phase space evolution involving microscale interactions); their impact on the polar wind itself requires a self‐consistent description. In this Letter, we discuss results of a self‐consistent hybrid model that explains the dayside observations. This model represents the first global kinetic collisional description for photoelectrons in a self‐consistent classical polar wind picture. In this model, photoelectrons are treated as test particles, ion properties are based on global kinetic collisional calculations, thermal electron features and the ambipolar field are determined by fluid calculations. The model provides the first global steady‐state polar wind solution that is continuous from the subsonic collisional regime at low altitude to the supersonic collisionless regime at high altitude. Also, the results are consistent with experiments in several aspects, such as order of magnitude of the ambipolar electric potential, qualitative features of the ion outflow characteristics, electron anisotropy and upwardly directed electron heat flux on the dayside.

Abstract. We investigate the effects of kinetic waveparticle interactions on the solar wind using a global hybrid model. The model follows the evolution of the particle distributions along an inhomogeneous field line under the influence of wave-particle interactions, an ambipolar electric field that is consistent with the particle distributions themselves, and Coulomb collisions. This represents the "first results" of global evolutionary study of the solar wind that take into account these kinetic effects. The model can account for the bulk acceleration of the solar wind, the preferential heating of the helium ions over the protons, as well as the occasionally observed double-peaked proton velocity distributions. the global evolution of the ion distributions is based on kinetic calculations that, among other major effects, also take into account the Coulomb interactions, including those among the same ion species. The suprathermal electrons, which are the tail portion of the thermal electron distribution at the lower boundary, are also described by a similar approach, except that they are treated as test particles due to their low relative density. The bulk thermal electrons, assumed to be in a drifting Maxwellian, and the arebipolar field are determined with a fluid approach. When combined with Monte Carlo modeling of ion resonant heating, the technique enables us not only to follow the global evolution of the solar wind particle distributions under the effect of wave-particle interactions, but also to determine the influence of the arebipolar electric field that is consistent with the distributions themselves. 3189

Linear mode conversion is considered between the ion-cyclotron and magnetosonic branches in a multispecies plasma with parallel magnetic field gradients. The results are interpreted in terms of ion conic heating. The mode-conversion coefficients are solved using perturbation theory, a phase integral approach, and saddle-point theory. These results are compared with numerical calculations. The coefficients thus obtained demonstrate that substantial coupling occurs between the four propagating modes, and a definite absorption occurs. Such absorption corresponds to ion heating and is, under realistic circumstances, sufficient to explain the outflow and heating of ionospheric oxygen.

[1] We perform intermittency analyses on the electric field data obtained by the SIERRA sounding rocket in the auroral zone. The electric field fluctuations are broadband, covering the extremely low-frequency range with a power-law relation, similar to the type of fluctuations commonly observed at various altitudes of the auroral region. Our preliminary analyses of the data based on the technique of probability distribution functions indicate that the electric field fluctuations are intermittent in the spacecraft frame. Using the methods of wavelet analyses and local intermittency measures, we determine the degree of intermittency of the fluctuations at various scales. It is found that the electric field fluctuations are more intermittent at smaller scales. Citation: Tam, S. W. Y., T. Chang, P. M.Kintner, and E. Klatt (2005), Intermittency analyses on the SIERRA measurements of the electric field fluctuations in the auroral zone, Geophys. Res. Lett., 32, L05109,