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| Titel |
Geomagnetic storm effects at F1-layer heights from incoherent scatter observations |
| VerfasserIn |
A. V. Mikhailov, K. Schlegel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 21, no. 2 ; Nr. 21, no. 2, S.583-596 |
| Datensatznummer |
250014576
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| Publikation (Nr.) |
 copernicus.org/angeo-21-583-2003.pdf |
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| Zusammenfassung |
Storm effects at F1-layer
heights (160–200 km) were analyzed for the first time using Millstone Hill
(mid-latitudes) and EISCAT (auroral zone) incoherent scatter (IS) observations.
The morphological study has shown both increases (positive effect) and
decreases (negative effect) in electron concentration. Negative storm effects
prevail for all seasons and show a larger magnitude than positive ones, the
magnitude of the effect normally increasing with height. At Millstone Hill the
summer storm effects are small compared to other seasons, but they are well
detectable. At EISCAT this summer decrease takes place only with respect to the
autumnal period and the autumn/spring asymmetry in the storm effects is well
pronounced. Direct and significant correlation exists between deviations in
electron concentration at the F1-layer heights and in the F2-layer maximum.
Unlike the F2-layer the F1-region demonstrates a relatively small reaction to
geomagnetic disturbances despite large perturbations in thermospheric
parameters. Aeronomic parameters extracted from IS observations are used to
explain the revealed morphology. A competition between atomic and molecular ion
contributions to Ne variations was found to be the main physical mechanism
controlling the F1-layer storm effect. The revealed morphology is shown to be
related with neutral composition (O, O2, N2) seasonal and
storm-time variations. The present day understanding of the F1-region formation
mechanisms is sufficient to explain the observed storm effects.
Key words. Atmospheric composition
and structure (thermosphere-composition and chemistry); ionosphere (ion
chemistry and composition; ionospheric disturbances) |
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