University of Oulu

Yagova, N., Kozlovsky, A., Fedorov, E., and Kozyreva, O.: Even moderate geomagnetic pulsations can cause fluctuations of foF2 frequency of the auroral ionosphere, Ann. Geophys., 39, 549–562, https://doi.org/10.5194/angeo-39-549-2021, 2021

Even moderate geomagnetic pulsations can cause fluctuations of foF2 frequency of the auroral ionosphere

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Author: Yagova, Nadezda1; Kozlovsky, Alexander2; Fedorov, Evgeny1;
Organizations: 1Laboratory of Physics of the Earth's Environment, Schmidt Institute of Physics of the Earth, Moscow, Russia
2Sodankylä Geophysical Observatory of the University of Oulu, Sodankylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2021070140817
Language: English
Published: Copernicus Publications, 2021
Publish Date: 2021-07-01
Description:

Abstract

The ionosonde at the Sodankylä Geophysical Observatory (SOD; 67∘ N, 27∘ E; Finland) routinely performs vertical sounding once per minute which enables the study of fast ionospheric variations at a frequency of the long-period geomagnetic pulsations Pc5–6/Pi3 (1–5 mHz). Using the ionosonde data from April 2014–December 2015 and colocated geomagnetic measurements, we have investigated a correspondence between the magnetic field pulsations and variations of the critical frequency of radio waves reflected from the ionospheric F2 layer (foF2). For this study, we have developed a technique for automated retrieval of the critical frequency of the F2 layer from ionograms. As a rule, the Pc5–6/Pi3 frequency band fluctuations in foF2 were observed at daytime during quiet or moderately disturbed space weather conditions. In most cases (about 80 %), the coherence between the foF2 variations and geomagnetic pulsations was low. However in some cases (specified as “coherent”) the coherence was as large as γ²≥0.5. The following conditions are favorable for the occurrence of coherent cases: enhanced auroral activity (6 h maximal auroral electrojet (AE) ≥800 nT), high solar wind speed (V>600 km/s), fluctuating solar wind pressure and northward interplanetary magnetic field. In the cases when the coherence was higher at shorter periods of oscillations, the magnetic pulsations demonstrated features typical for the Alfvén field line resonance.

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Series: Annales geophysicae
ISSN: 0992-7689
ISSN-E: 1432-0576
ISSN-L: 0992-7689
Volume: 39
Issue: 3
Pages: 549 - 562
DOI: 10.5194/angeo-39-549-2021
OADOI: https://oadoi.org/10.5194/angeo-39-549-2021
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Subjects:
Funding: This research has been supported by the Academy of Finland (grant nos. 298578 and 310348), the Russian Foundation for Basic Research (RFBR) (grant no. 20-05-00787) and the state contract with IPE (NY, EF).
Academy of Finland Grant Number: 298578
310348
Detailed Information: 298578 (Academy of Finland Funding decision)
310348 (Academy of Finland Funding decision)
Dataset Reference: Data used in the paper are available at:
  https://www.sgo.fi/pub/AnnGeo_2021_39_1/CODES/
Copyright information: © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.
  https://creativecommons.org/licenses/by/4.0/