O+ ions in the polar wind


  • A. R. Barakat,

  • R. W. Schunk


A semikinetic model was used to describe the steady state collisionless flow of the polar wind along diverging geomagnetic field lines at high latitudes. Emphasis was given to studying the behavior of O+ ions for a wide range of boundary conditions at the baropause (4500 km). The main result obtained was that for high electron temperatures (Te ∼ 10,000 K) O+ is not gravitationally bound and significant escape fluxes (∼107 cm−2 s−1) of suprathermal (∼2 eV) O+ ions occur. The O+ flow is supersonic over most of the altitude range considered, and O+ Mach numbers as large as 20 are predicted at 10 RE. Also, depending on the boundary conditions, the O+ density can be comparable to or greater than the H+ density at high altitudes above the baropause when the electron temperature is high.