Publisher： John Wiley & Sons Inc
E-ISSN： 1944-8007|41|11|3752-3758
ISSN： 0094-8276
Source： GEOPHYSICAL RESEARCH LETTERS, Vol.41, Iss.11, 2014-06, pp. : 3752-3758
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Abstract
AbstractBeams of H+, He+, and O+ ions have been observed when the four Cluster satellites crossed the high‐latitude plasma sheet boundary layer at ∼4 RE. These beams appear as inverted‐V structures in the energy flux time spectrograms. The pitch angles of the beams range from ∼0 to 30° indicating the ions are streaming along the magnetic field out of the ionosphere. The streaming velocity is a few tens of km/s to several hundred km/s, consistent with the beams having gone through a potential drop of several tens of eV to a few keV. These beams are intense with beam to ambient density ratios, δnb/nT, as large as ∼0.3. The beams are hotter than the ionospheric ion thermal energy, indicating the ions have been heated while accelerated along the magnetic field. We present first results that show the ions tend to be hotter at the peak (several hundred eV) than at the start of the inverted‐V structures (a few tens of eV). These results interpreted in terms of a U‐shaped potential structure indicate the hottest ions come from the central region where the potential difference is maximum.
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