New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5
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 ∼...
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ftdoajarticles:oai:doaj.org/article:558c577faaae4e92938e617df28c1550 2023-05-15T17:42:40+02:00 New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 J. Manninen N. Kleimenova T. Turunen L. Gromova 2018-06-01T00:00:00Z https://doi.org/10.5194/angeo-36-915-2018 https://doaj.org/article/558c577faaae4e92938e617df28c1550 EN eng Copernicus Publications https://www.ann-geophys.net/36/915/2018/angeo-36-915-2018.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-36-915-2018 0992-7689 1432-0576 https://doaj.org/article/558c577faaae4e92938e617df28c1550 Annales Geophysicae, Vol 36, Pp 915-923 (2018) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2018 ftdoajarticles https://doi.org/10.5194/angeo-36-915-2018 2023-01-08T01:30:31Z 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 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 <q>bullets</q> 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 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 Directory of Open Access Journals: DOAJ Articles Annales Geophysicae 36 3 915 923 |
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Directory of Open Access Journals: DOAJ Articles |
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Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
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Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 J. Manninen N. Kleimenova T. Turunen L. Gromova New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5 |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
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 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 <q>bullets</q> 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 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 |
J. Manninen N. Kleimenova T. Turunen L. Gromova |
author_facet |
J. Manninen N. Kleimenova T. Turunen L. Gromova |
author_sort |
J. Manninen |
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 |
https://doi.org/10.5194/angeo-36-915-2018 https://doaj.org/article/558c577faaae4e92938e617df28c1550 |
genre |
Northern Finland |
genre_facet |
Northern Finland |
op_source |
Annales Geophysicae, Vol 36, Pp 915-923 (2018) |
op_relation |
https://www.ann-geophys.net/36/915/2018/angeo-36-915-2018.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-36-915-2018 0992-7689 1432-0576 https://doaj.org/article/558c577faaae4e92938e617df28c1550 |
op_doi |
https://doi.org/10.5194/angeo-36-915-2018 |
container_title |
Annales Geophysicae |
container_volume |
36 |
container_issue |
3 |
container_start_page |
915 |
op_container_end_page |
923 |
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1766144562022055936 |