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| Titel |
Longitudinal (UT) effect in the onset of auroral disturbances over two solar cycles as deduced from the AE-index |
| VerfasserIn |
L. A. Hajkowicz |
| 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 ; 16, no. 12 ; Nr. 16, no. 12, S.1573-1579 |
| Datensatznummer |
250013595
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| Publikation (Nr.) |
 copernicus.org/angeo-16-1573-1998.pdf |
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| Zusammenfassung |
Statistical study on the universal time
variations in the mean hourly auroral electrojet index (AE-index) has been
undertaken for a 21 y period over two solar cycles (1957–1968 and 1978–1986).
The analysis, applied to isolated auroral substorm onsets (inferred from rapid
variations in the AE-index) and to the bulk of the AE data, indicates that the
maximum in auroral activity is largely confined to 09–18 UT, with a distinct
minimum at 03–06 UT. The diurnal effect was clearly present throughout all
seasons in the first cycle but was mainly limited to northern winter in the
second cycle. Severe storms (AE > 1000 nT) tended to occur between 9–18 UT
irrespective of the seasons whereas all larger magnetic disturbances (AE >
500 nT) tended to occur in this time interval mostly in winter. On the whole the
diurnal trend was strong in winter, intermediate at equinox and weak in summer.
The implication of this study is that Eastern Siberia, Japan and Australia are
mostly at night, during the period of maximum auroral activity whereas Europe
and Eastern America are then mostly at daytime. The minimum of auroral activity
coincides with near-midnight conditions in Eastern America. It appears that the
diurnal UT distribution in the AE-index reflects a diurnal change between
interplanetary magnetic field orientation and the Earth's magnetic dipole
inclination.
Key words. Ionosphere (auroral ionosphere) ·
Magnetospheric physics (auroral phenomena; storms and substorms). |
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