Characteristics of thermal ion outflows in the polar cap according to data of the <Emphasis Type="Italic">Interball-2</Emphasis> satellite |
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Authors: | D V Chugunin |
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Institution: | 1.Space Research Institute,Russian Academy of Sciences,Moscow,Russia |
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Abstract: | Characteristics of polar wind fluxes at a height of ∼20000 km measured by the Hyperboloid mass-spectrometer installed onboard
the Interball-2 satellite are presented in the paper. The characteristics are presented for the upwelling flows of ionospheric ions H+, He+, and O+ from the sunlit polar cap in the period of solar activity minimum. Orbit segments with minimal precipitation of magnetospheric
ions and electrons were preliminarily selected, and the measurements where the fluxes of ions coming from the cusp/cleft were
excluded as carefully as possible. Thus, the densities, field-aligned velocities, and temperatures of ions in the regions
where fluxes of polar wind could be detected with the maximal probability degree are presented in the paper. It is found that
cases when only H+ ions are reaching the detector are with high probability the polar wind outflows. Their characteristics agree well with the
Tube-7 hydrodynamic model and are as follows: n ≈ 1.5 cm−3, V
∥ ∼ 21 km/s; T
∥ = 3500 K, and T
⊥ = 2000 K. In cases when He+ and O+ ions are also detected, the temperatures are substantially higher than the model ones, and the measured field-aligned velocities
of O+ fluxes are several times higher than the model ones. Moreover, it was revealed that the polar wind outflows are predominantly
observed in the polar cap regions where the polar rain fluxes are very small. |
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