University of Oulu

Bezděková, B., Němec, F. & Manninen, J. Ground-based VLF wave intensity variations investigated by the principal component analysis. Earth Planets Space 74, 30 (2022).

Ground-based VLF wave intensity variations investigated by the principal component analysis

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Author: Bezděková, Barbora1; Němec, František1; Manninen, Jyrki2
Organizations: 1Faculty of Mathematics and Physics, Charles University, V Holešovičkách 747/2, 18000, Prague, Czech Republic
2Sodankylä Geophysical Observatory, University of Oulu, Tähteläntie 62, 99600, Sodankylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.1 MB)
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Language: English
Published: Springer Nature, 2022
Publish Date: 2022-05-24


Very low frequency wave intensity variations measured by the Kannuslehto station, Finland in the frequency range 0–12 kHz between 2016 and 2020 are analyzed by the principal component analysis (PCA). As the analyzed ground-based measurements are basically continuous, the length of individual basis vectors entering into PCA is fundamentally arbitrary. To better characterize both long- and short-period variations, two PCAs with different lengths of the basis vectors are eventually performed. Specifically, either daily frequency–time spectrograms or individual frequency spectra are chosen as the PCA basis vectors. Analysis of the first three principal components shows substantial variations of the wave intensity due to seasonal and local time effects. Intensity variations related to the geomagnetic activity characterized by Kp and AE indices and standard deviation of the magnetic field magnitude are less significant. Moreover, PCA allows one to distinguish between nighttime and daytime Kannuslehto variations and study them independently. Solar and geomagnetic activity effects on the daytime and nighttime measurements are discussed. Wave intensity variations related to substorm occurrence are also analyzed.

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Series: Earth, planets and space
ISSN: 1343-8832
ISSN-E: 1880-5981
ISSN-L: 1343-8832
Volume: 74
Article number: 30
DOI: 10.1186/s40623-022-01588-4
Type of Publication: A1 Journal article – refereed
Field of Science: 1171 Geosciences
Funding: This research was supported by GACR Grants 20-09671S and 21-01813S.
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