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| Titel |
Pre-Storm Ionospheric Oxygen Ions between the Ionosphere and the Inner Magnetosphere |
| VerfasserIn |
A. W. Yau, A. Howarth, W. K. Peterson, T. Abe |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250061406
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| Zusammenfassung |
| The prompt appearance of energetic O+ ions in the ring current in the growth phase of a magnetic storm raises the interesting question of the possible role of O+ ions between the ionosphere and the plasma sheet and ring current immediately preceding the main phase of a magnetic storm. We examine oxygen ion transport from the high-altitude polar ionosphere in the quiet-time periods immediately preceding a series of five large magnetic storms (Dst < -100 nT) in Solar Cycle 23, using single-particle trajectory simulations in conjunction with Akebono ion measurements and related IMF and convection electric field data. Observed low-energy O+ ions on Akebono in the quiet-time high-altitude auroral and polar cap ionosphere (7000 km) are found to have temperatures of about 0.2-0.3 eV and flow velocities of a few km/s, and a portion of the ions undergo centrifugal acceleration at higher altitudes (above about 3 Earth radii (altitude)), resulting in a low but non-negligible O+ ion flux between the ionosphere and the plasma sheet and ring current that is dependent on IMF as well as Kp: up 30% of the observed low-energy O+ ions reach the plasma sheet, and more of the ions reach the dusk than dawn, corresponding to an O+ mass source rate of ~ 0.14 kg/s and a “plasma sheet filling time” of ~6.7 hr near solar maximum, assuming a plasma sheet oxygen density of 0.1 per cc. |
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