Global Neutral Polar Wind Model

The polar wind is an outflow of thermal ions from high-latitudes along geomagnetic field lines that are connected to the interplanetary magnetic field (IMF), or on field lines that are stretched out in the anti-sunward direction forming the magnetotail. The ions in the polar wind are highly dependent on convection and their outflow dynamics are modified by the heat input of precipitating electrons in the auroral zone. Charge exchange occurs between the outflowing ions and the neutral thermal and geocoronal atoms, producing neutral stream particles. A new three-dimensional model of the neutral polar wind has been developed which takes into account the convecting ion polar wind and heating due to precipitating electrons in the auroral zone, along with charge exchange between the ion polar wind and the background thermal and geocoronal neutral atoms. Three-dimensional simulations for both northward and southward IMF conditions show that over the polar caps the neutral polar wind particles exhibit extremely large fluxes in both the horizontal and vertical directions, and to a fixed observer it would appear that the neutral polar wind particles are moving in all directions. The results also show that the heating that occurs during geomagnetic storms leads to a significant coupling between the ionosphere and magnetosphere via both ion and neutral particles. For northward IMF, sunward streams of neutrals are created as a result of the sunward plasma convection.