University of Oulu

Martinez-Calderon, C., Manninen, J. K., Manninen, J. T., & Turunen, T. (2023). Statistics of unusual naturally occurring VLF radio emissions termed bursty-patches observed at Kannuslehto, Finland. Journal of Geophysical Research: Space Physics, 128, e2022JA030792.

Statistics of unusual naturally occurring VLF radio emissions termed bursty-patches observed at Kannuslehto, Finland

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Author: Martinez-Calderon, C.1; Manninen, J. K.2; Manninen, J. T.;
Organizations: 1Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan
2Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 9.8 MB)
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Language: English
Published: American Geophysical Union, 2023
Publish Date: 2023-09-01


We report the results from a statistical study of a new type of naturally occurring, but differently structured very low frequency (VLF) radio waves called “VLF bursty-patches.” Their main characteristic is that they are detected at frequencies above the electron gyrofrequency (fce) in the equatorial plane for the L-shell of observation. Here we use the data from the station of Kannuslehto, Finland (KAN, MLAT = 64.4°N, L = 5.5) with fce ∼ 5–6 kHz where VLF bursty-patches are commonly detected on at least 43% of its campaign days. We analyzed all available data for 2017 (∼8 months) separating the observations by spectral type, periodicity, number of bursts, observed frequency, and accompanying usual VLF emissions at lower frequencies (f < 6 kHz). We found that the overall highest occurrence rate is in the morning sector (05–12 MLT) correlating with general VLF occurrence rate at KAN (07–13 MLT, MLT = UT + 1.5 hr). Grouping usual VLF emissions and bursty-patches showing similar spectral features, suggests that both groups are being generated by the same mechanisms (e.g., temperature anisotropy magnetospheric plasma distribution). However, unlike the situation for usual VLF emissions, the daily occurrence of bursty-patches did not show a clear relationship with AE index. Superposed epoch analysis of magnetic components from the Sodankylä magnetometer (∼45 km from KAN) shows that VLF bursty-patches are detected when the horizontal component of the magnetic field shows minimum variations. This suggests that propagation to the ground of bursty-patches is conditioned to localized low variations of magnetic activity.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 128
Issue: 1
Article number: e2022JA030792
DOI: 10.1029/2022JA030792
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Instrumentation and data analysis at KAN are funded by the Sodankylä Geophysical Observatory (SGO) and the University of Oulu. CMC research and analysis is funded by Nagoya University and the PWING project (JSPS 16H06286). CMC would like to thank the ArcI International Visiting Grants committee for their travel support to work with data in-situ in Finland.
Dataset Reference: Power spectrum density of VLF data from KAN used in this analysis is publicly available as quick look plots in 1-hr formats at
Copyright information: © 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.