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| Titel |
New type of ensemble of quasi-periodic, long-lasting VLF emissions at the auroral zone |
| VerfasserIn |
J. Manninen, N. G. Kleimenova, O. V. Kozyreva |
| 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 ; 30, no. 12 ; Nr. 30, no. 12 (2012-12-11), S.1655-1660 |
| Datensatznummer |
250017292
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1655-2012.pdf |
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| Zusammenfassung |
| A new type of the series of quasi-periodic (QP) very low
frequency (VLF) emissions in frequency range of 1–5 kHz, and not associated
with geomagnetic pulsations, has been discovered at auroral latitudes
(L = 5.3) during the Finnish VLF campaign (held in December 2011). At least
five unusually spectacular events, each with a duration of several hours,
have been observed during the night under conditions of quiet geomagnetic
activity (Kp = 0–1), although QPs usually occur during the daytime. Contrary
to the QP emissions typically occurring during the day, the spectral
structure of these QP events represented an extended, complicated sequence
of repeated discrete rising VLF signals. Their duration was about 2–3 min
each, with the repetition periods ranging from ~1 min to
~10 min. Two such nighttime non-typical events are reported
in this paper. The fine structure of the separated QP elements may represent
a mixture of the different frequency band signals, which seem to have
independent origins. It was found that the periodic signals with lower
frequency appear to trigger the strong dispersive upper frequency
signals. The temporal dynamics of the spectral
structure of the QPs studied were significantly controlled by some
disturbances in the solar wind and interplanetary magnetic field (IMF). This finding is very important for
future theoretical investigations because the generation mechanism of this
new type of QP emissions is not yet understood. |
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