The neutral polar wind

L. C. Gardner and R. W. Schunk 
Center for Atmospheric and Space Sciences, Utah State University, Logan, UT

The classical polar wind is an ambipolar outflow of ions from high latitudes along
open geomagnetic field lines. The polar wind consists of light thermal ions (H +,
He+), and energetic light and heavy ions (H +, He+, O+). The characteristics of
these ions have been studied quite extensively since the 1960Ís. In just the last
20 years, however, energetic neutral atoms (ENA ïs) that are produced in charge
exchange reactions between the singly ionized polar wind ions and the surrounding
neutral atoms have been used as a means to remotely probe plasma populations.
Recent estimates for neutral outflow integrated fluxes from the LENA instrument on
board the IMAGE spacecraft have shown values of 1-4x10 **9 cm-2/s, with a
considerable diurnal variation. A theoretical model has been used in this study
that is similar to the high-altitude hydrodynamic polar wind model developed at
Utah State University, but it has been expanded to include the effects of neutral
stream particles so that the characteristics of the neutral polar wind can be
elucidated. The neutral polar wind model results show a high neutral outflow flux
on the order of 10**9 cm-2/s.

_______________ 
Presented at the 35th COSPAR Scientific Assembly, Paris, France, July 18-25, 2004.