New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5
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 Finlan...
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ftunivoulu:oai:oulu.fi:nbnfi-fe2018110547342 2023-07-30T04:05:49+02:00 New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 Manninen, J. (Jyrki) Kleimenova, N. (Natalia) Turunen, T. (Tauno) Gromova, L. (Liudmila) 2018 application/pdf http://urn.fi/urn:nbn:fi-fe2018110547342 eng eng Copernicus Publications info:eu-repo/semantics/openAccess © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. https://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2018 ftunivoulu 2023-07-08T19:55:17Z 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. Article in Journal/Newspaper Northern Finland Jultika - University of Oulu repository |
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Open Polar |
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Jultika - University of Oulu repository |
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ftunivoulu |
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English |
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. |
format |
Article in Journal/Newspaper |
author |
Manninen, J. (Jyrki) Kleimenova, N. (Natalia) Turunen, T. (Tauno) Gromova, L. (Liudmila) |
spellingShingle |
Manninen, J. (Jyrki) Kleimenova, N. (Natalia) Turunen, T. (Tauno) Gromova, L. (Liudmila) New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
author_facet |
Manninen, J. (Jyrki) Kleimenova, N. (Natalia) Turunen, T. (Tauno) Gromova, L. (Liudmila) |
author_sort |
Manninen, J. (Jyrki) |
title |
New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
title_short |
New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
title_full |
New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
title_fullStr |
New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
title_full_unstemmed |
New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
title_sort |
new high-frequency (7–12 khz) quasi-periodic vlf emissions observed on the ground at l ∼ 5.5 |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
http://urn.fi/urn:nbn:fi-fe2018110547342 |
genre |
Northern Finland |
genre_facet |
Northern Finland |
op_rights |
info:eu-repo/semantics/openAccess © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. https://creativecommons.org/licenses/by/4.0/ |
_version_ |
1772818034652610560 |