Global neutral polar wind model

Abstract

[1] The neutral polar wind shows a highly dynamic structure that depends on the characteristics of convection and precipitation. The ions in the polar wind are highly dependent on convection electric fields at high latitudes, and their outflow dynamics are modified by the heat input of precipitating electrons in the auroral zone. 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. The results 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.

Ion and neutral polar winds for northward interplanetary magnetic field conditions

“…This simulation is a continuation of the magnetic storm simulation of Gardner and Schunk (2005) taking up at the end of the previous simulation, and thus the density enhancements at high-altitude due to the magnetic storm are still present at the start of this simulation. Fig.…”

“…where n represents number density, u velocity, m mass, e charge, P pressure tensor, G gravity, E electric field, B magnetic field, j can represent either ions or neutrals with E and B dropping from the momentum equation for the neutrals, and the righthand terms represent production, loss, and collisions as discussed in Gardner and Schunk (2005). Empirical model inputs for the convection electric fields (Weimer, 2001) and electron precipitation (Hardy et al, 1985) are used in order to allow for ion convection in the polar cap and ion heating in the auroral oval, respectively.…”

“…In a previous study, an idealized magnetic storm was simulated (Gardner and Schunk, 2005). For this study, relatively simple variations of the IMF, solar wind, and K p values were adopted in order to simulate northward IMF conditions (Fig.…”

“…However, the impact of neutral atoms outflowing from the ionosphere into the magnetosphere has had relatively little attention. Recent studies by Gardner and Schunk (2004, 2005, 2006 exchange between the polar wind and background neutral atoms, and termed the neutral outflow from high latitudes the 'neutral polar wind'.…”

“…In a previous study of an idealized magnetic storm under southward IMF conditions, we modeled the ion and neutral polar winds using our threedimensional model (Gardner and Schunk, 2005). Fig.…”