| Autor: |
Manninen, Jyrki, Kleimenova, Natalia, Turunen, Tauno, Gromova, Liudmila |
| Předmět: |
|
| Zdroj: |
Annales Geophysicae (ANGEO) (09927689); 2018, Vol. 36 Issue 3, p915-923, 9p |
| Abstrakt: |
We reveal previously unknown quasi-periodic (QP) very low frequency (VLF) emissions at the unusually high-frequency band of ~7-12 kHz by applying the digital filtering of strong atmospherics to the ground-based VLF data recorded at Kannuslehto station (KAN). It is located in northern Finland at L ~ 5:5. The frequencies of QP emissions are much higher than the equatorial electron gyrofrequency at L ~ 5:5. Thus, these emissions must have been generated at much lower L shells than KAN. Two highfrequency QP emission events have been studied in detail. The emissions were right-hand polarized waves indicating an overhead location of the exit area of waves in the ionosphere. In one event, the spectral-temporal forms of the emissions looked like a series of giant "bullets" due to the very abrupt cessation. Unfortunately, we could not explain such a strange dynamic spectral shape of the waves. In the second event, the modulation period was about 3 min under the absence of simultaneous geomagnetic pulsations. The studied emissions lasted about 4 h and were observed under the very quiet geomagnetic activity. The adequate mechanisms of the generation and propagation of the revealed highfrequency QP emissions have not yet been established. We speculate that studied QP emissions can be attributed to the auto-oscillations of the cyclotron instability in the magnetospheric plasma maser. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
|
Nepřihlášeným uživatelům se plný text nezobrazuje |
K zobrazení výsledku je třeba se přihlásit.
|
