Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland
Abstract Unexpected short patches of natural VLF emissions at f > 5 kHz have been observed at the ground station of Kannuslehto (KAN, L ~ 5.5) in Northern Finland. In contrast with usual VLF emissions (e.g., chorus, hiss, and quasiperiodic emissions) these high-frequency bursty-patches are observ...
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ftunivoulu:oai:oulu.fi:nbnfi-fe2023052648425 2023-07-30T04:05:49+02:00 Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland Manninen, J. (J.) Kleimenova, N. G. (N. G.) Martinez-Calderon, C. (C.) Gromova, L. I. (L. I.) Turunen, T. (T.) 2023 application/pdf http://urn.fi/urn:nbn:fi-fe2023052648425 eng eng Springer Nature info:eu-repo/semantics/openAccess © The Author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. https://creativecommons.org/licenses/by/4.0/ Electron cyclotron interaction Geomagnetic disturbances VLF waves info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2023 ftunivoulu 2023-07-08T20:01:54Z Abstract Unexpected short patches of natural VLF emissions at f > 5 kHz have been observed at the ground station of Kannuslehto (KAN, L ~ 5.5) in Northern Finland. In contrast with usual VLF emissions (e.g., chorus, hiss, and quasiperiodic emissions) these high-frequency bursty-patches are observed at frequencies higher than half of the equatorial electron gyro-frequency of the L shell of KAN. Moreover, most of these waves reached frequencies above the local equatorial electron gyrofrequency at L = 5.5. Thus, they cannot be attributed to the classical theory of electron-cyclotron interaction. We present a review of VLF bursty-patches at KAN during winters 2011–2021. These emissions have rarely been observed as they are usually hidden by sferics originating from lightning discharges. Therefore, a special numeric filtering technique was used to reduce noise from sferics. VLF bursty-patches typically occur as sequences of short right-hand polarized bursts separated by a few minutes and lasting several hours. Here, we discuss the spectral structure of long-lasting bursty-patches (6 + hours) and the properties of individual patches. We established two categories: (1) “triggered-like” hiss-like bursts at f ~ 4–7 kHz with a very abrupt onset and detected under quiet geomagnetic conditions, and (2) “dash-like” emissions at f > 6 kHz that resemble narrowband hiss and observed under moderate activity. Even though VLF bursty-patches in winters 2011–2021 were observed under weak or slightly disturbed magnetic activity, their annual cyclical occurrence was similar to variations in solar activity. The nature of these VLF patches has not been established yet, but they appear to be generated at L shells lower than that of KAN. Their exact generation region and propagation behavior remain unknown, with further theoretical and experimental research being required. Article in Journal/Newspaper Northern Finland Jultika - University of Oulu repository |
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Open Polar |
collection |
Jultika - University of Oulu repository |
op_collection_id |
ftunivoulu |
language |
English |
topic |
Electron cyclotron interaction Geomagnetic disturbances VLF waves |
spellingShingle |
Electron cyclotron interaction Geomagnetic disturbances VLF waves Manninen, J. (J.) Kleimenova, N. G. (N. G.) Martinez-Calderon, C. (C.) Gromova, L. I. (L. I.) Turunen, T. (T.) Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland |
topic_facet |
Electron cyclotron interaction Geomagnetic disturbances VLF waves |
description |
Abstract Unexpected short patches of natural VLF emissions at f > 5 kHz have been observed at the ground station of Kannuslehto (KAN, L ~ 5.5) in Northern Finland. In contrast with usual VLF emissions (e.g., chorus, hiss, and quasiperiodic emissions) these high-frequency bursty-patches are observed at frequencies higher than half of the equatorial electron gyro-frequency of the L shell of KAN. Moreover, most of these waves reached frequencies above the local equatorial electron gyrofrequency at L = 5.5. Thus, they cannot be attributed to the classical theory of electron-cyclotron interaction. We present a review of VLF bursty-patches at KAN during winters 2011–2021. These emissions have rarely been observed as they are usually hidden by sferics originating from lightning discharges. Therefore, a special numeric filtering technique was used to reduce noise from sferics. VLF bursty-patches typically occur as sequences of short right-hand polarized bursts separated by a few minutes and lasting several hours. Here, we discuss the spectral structure of long-lasting bursty-patches (6 + hours) and the properties of individual patches. We established two categories: (1) “triggered-like” hiss-like bursts at f ~ 4–7 kHz with a very abrupt onset and detected under quiet geomagnetic conditions, and (2) “dash-like” emissions at f > 6 kHz that resemble narrowband hiss and observed under moderate activity. Even though VLF bursty-patches in winters 2011–2021 were observed under weak or slightly disturbed magnetic activity, their annual cyclical occurrence was similar to variations in solar activity. The nature of these VLF patches has not been established yet, but they appear to be generated at L shells lower than that of KAN. Their exact generation region and propagation behavior remain unknown, with further theoretical and experimental research being required. |
format |
Article in Journal/Newspaper |
author |
Manninen, J. (J.) Kleimenova, N. G. (N. G.) Martinez-Calderon, C. (C.) Gromova, L. I. (L. I.) Turunen, T. (T.) |
author_facet |
Manninen, J. (J.) Kleimenova, N. G. (N. G.) Martinez-Calderon, C. (C.) Gromova, L. I. (L. I.) Turunen, T. (T.) |
author_sort |
Manninen, J. (J.) |
title |
Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland |
title_short |
Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland |
title_full |
Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland |
title_fullStr |
Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland |
title_full_unstemmed |
Unexpected VLF bursty-patches above 5 kHz:a review of long-duration VLF series observed at Kannuslehto, Northern Finland |
title_sort |
unexpected vlf bursty-patches above 5 khz:a review of long-duration vlf series observed at kannuslehto, northern finland |
publisher |
Springer Nature |
publishDate |
2023 |
url |
http://urn.fi/urn:nbn:fi-fe2023052648425 |
genre |
Northern Finland |
genre_facet |
Northern Finland |
op_rights |
info:eu-repo/semantics/openAccess © The Author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. https://creativecommons.org/licenses/by/4.0/ |
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