1998•Geophysical Research LettersRequires access
Concurrent observations of solar wind oxygen by Geotail in the magnetosphere and wind in interplanetary space
S. P. Christon, C. M. S. Cohen, G. Gloeckler, T. E. Eastman, A. B. Galvin, F. M. Ipavich, Yuan‐Kuen Ko, A. T. Y. Lui, Rex Lundgren, R. W. McEntire, E. C. Roelof, D. J. Williams
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Abstract
We present an initial report on the first direct, concurrent measurements of solar wind oxygen (O) charge state variations inside and outside Earth's magnetosphere. On 10‐11 Jan 1997 a magnetic cloud, with a spatial scale of at least ∼100 R E engulfed the magnetosphere. At ∼1200 UT on 10 Jan 1997, the Wind/SWICS ion charge‐state spectrometer, at ∼90 R E upstream of Earth, detected an increase in the solar wind O charge state ratio Γ o = (O +7 + O +8 ) / O +6 at ∼0.5‐30 keV/e which persisted until ∼2400 UT on 10 Jan 1997. After ∼1110 UT on 10 Jan 1997, Geotail was in and near the mid‐afternoon to dusk magnetosphere. The ∼9.4‐210 keV/e Γ o value from the Geotail/STICS spectrometer showed a longer‐term, gradual increase over ∼8–10 hr. Then, after ∼0600 UT on 11 Jan 1997, Wind observed a Γ o decrease at a high speed solar wind stream onset. About 6 hr later Γ o decreased promptly at Geotail during a plasma sheet substorm injection. Both instances are long durations compared to nominal 3‐hr substorm time‐scales.