University of Oulu

Manninen, J., Kleimenova, N., Turunen, T., and Gromova, L.: New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L  ∼  5.5, Ann. Geophys., 36, 915-923, https://doi.org/10.5194/angeo-36-915-2018, 2018

New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L  ∼  5.5

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Author: Manninen, Jyrki1; Kleimenova, Natalia2,3; Turunen, Tauno1;
Organizations: 1Sodankylä Geophysical Observatory, Sodankylä, Finland
2Schmidt Institute of Physics of the Earth RAN, Moscow, Russia
3Space Research Institute RAN, Moscow, Russia
4Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAN, Moscow, Troitsk, Russia
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 12.5 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2018110547342
Language: English
Published: Copernicus Publications, 2018
Publish Date: 2018-11-05
Description:

Abstract

We reveal previously unknown quasi-periodic (QP) very low frequency (VLF) emissions at the unusually high-frequency band of  ∼ 7–12kHz 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 high-frequency 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 3min under the absence of simultaneous geomagnetic pulsations. The studied emissions lasted about 4h and were observed under the very quiet geomagnetic activity. The adequate mechanisms of the generation and propagation of the revealed high-frequency 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.

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Series: Annales geophysicae
ISSN: 0992-7689
ISSN-E: 1432-0576
ISSN-L: 0992-7689
Volume: 36
Pages: 915 - 923
DOI: 10.5194/angeo-36-915-2018
OADOI: https://oadoi.org/10.5194/angeo-36-915-2018
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Subjects:
Funding: The research was supported by the Academy of Finland (grant no. 287988) during the stays of Natalia Kleimenova and Liudmila Gromova in Sodankylä. The work by Natalia Kleimenova was partly supported by the Program of Presidium of Russian Academy of Science no. 28.
Academy of Finland Grant Number: 287988
Detailed Information: 287988 (Academy of Finland Funding decision)
Copyright information: © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License.
  https://creativecommons.org/licenses/by/4.0/