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| Titel |
New results of structured VLF emissions observed simultaneously at two closely located stations near L ~ 5.5 |
| VerfasserIn |
J. Manninen, N. G. Kleimenova, Yu. V. Fedorenko, P. A. Bespalov, T. Turunen |
| 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 ; 32, no. 9 ; Nr. 32, no. 9 (2014-09-18), S.1163-1167 |
| Datensatznummer |
250121110
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1163-2014.pdf |
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| Zusammenfassung |
| Simultaneous records of VLF (very low frequencies) emissions have been carried out at two
ground-based stations located at similar geomagnetic latitudes near
L ~ 5.5 and spaced in the longitude by ~ 400 km, Kannuslehto
(KAN) in Finland and Lovozero (LOZ) in Russia, using quite similar VLF
receivers with two calibrated orthogonal air-core loop antennas. We found
that the general spectral properties of the VLF chorus emissions at these
two stations were similar and typically have right-hand polarization. Contrary to VLF chorus, the
short-period VLF emissions (periodic emissions, PE) in which separated
spectral elements are repeated with the periodicity of 3–4 s were mostly
left-hand polarized. Usually, these waves propagated in the north–south
direction. We suppose that PEs are generated inside of the plasmasphere by
the cyclotron instability under a quasi-linear relaxation of the energetic
electron distribution function. However, sometimes PE occurred only at an
individual station. We speculated that this could be due to the influence of
the local inhomogeneities to the VLF waves during the propagation through the
ionospheric trough to the ground. Unusual series of short-duration
(10–100 s) bursts of VLF emissions, lasting several hours, were also found
in the morning under very quiet geomagnetic conditions (Kp ~ 0–1).
Generally, these emissions were observed simultaneously at KAN and LOZ
showing both right-hand and left-hand polarization, and different arrival
directions provided the rather extended ionospheric exit area. |
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