University of Oulu

Demekhov, A. G., Manninen, J., Santolík, O., & Titova, E. E. (2017). Conjugate ground‐spacecraft observations of VLF chorus elements. Geophysical Research Letters, 44, 11,735– 11,744.

Conjugate ground‐spacecraft observations of VLF chorus elements

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Author: Demekhov, A. G.1,2; Manninen, J.3; Santolík, O.4,5;
Organizations: 1Polar Geophysical Institute, Apatity, Russia
2Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia
3Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
4Institute of Atmospheric Physics, Czech Academy of Sciences, Prague, Czech Republic
5Faculty of Mathematics and Physics, Charles University in Prague, Prague, Czech Republic
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.5 MB)
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Language: English
Published: American Geophysical Union, 2017
Publish Date: 2019-09-25


We present results of simultaneous observations of VLF chorus elements at the ground‐based station Kannuslehto in Northern Finland and on board Van Allen Probe A. Visual inspection and correlation analysis of the data reveal one‐to‐one correspondence of several (at least 12) chorus elements following each other in a sequence. Poynting flux calculated from electromagnetic fields measured by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probe A shows that the waves propagate at small angles to the geomagnetic field and oppositely to its direction, that is, from northern to southern geographic hemisphere. The spacecraft was located at L≃4.1 at a geomagnetic latitude of −12.4 close to the plasmapause and inside a localized density inhomogeneity with about 30% density increase and a transverse size of about 600 km. The time delay between the waves detected on the ground and on the spacecraft is about 1.3 s, with ground‐based detection leading spacecraft detection. The measured time delay is consistent with the wave travel time of quasi‐parallel whistler‐mode waves for a realistic profile of the plasma density distribution along the field line. The results suggest that chorus discrete elements can preserve their spectral shape during a hop from the generation region to the ground followed by reflection from the ionosphere and return to the near‐equatorial region.

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Series: Geophysical research letters
ISSN: 0094-8276
ISSN-E: 1944-8007
ISSN-L: 0094-8276
Volume: 44
Issue: 23
Pages: 11,735 - 11,744
DOI: 10.1002/2017GL076139
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Comparison of spacecraft and ground‐based data (A. D. and E. T.) was supported by the Russian Science Foundation (project 15‐12‐20005). The work on ground‐based data was supported by the Academy of Finland under grant 294931. Spacecraft data analysis (O. S.) was supported by MŠMT ČR through the LTAUSA17070 project and by the Praemium Academiae Award from The Czech Academy of Sciences.
Academy of Finland Grant Number: 294931
Detailed Information: 294931 (Academy of Finland Funding decision)
Dataset Reference: RBSP data used in this paper can be found in the EMFISIS ( archive. KAN data are available at
Copyright information: © 2017. American Geophysical Union. All Rights Reserved.