University of Oulu

Demekhov, A. G., Titova, E. E., Maninnen, J., Pasmanik, D. L., Lubchich, A. A., Santolík, O., et al. (2020). Localization of the source of quasiperiodic VLF emissions in the magnetosphere by using simultaneous ground and space observations: A case study. Journal of Geophysical Research: Space Physics, 125, e2020JA027776. https://doi.org/10.1029/2020JA027776

Localization of the source of quasiperiodic VLF emissions in the magnetosphere by using simultaneous ground and space observations : a case study

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Author: Demekhov, A. G.1,2; Titova, E. E.1,3; Maninnen, J.4;
Organizations: 1Polar Geophysical Institute, Apatity, Russia
2Institute of Applied Physics, RAS, Nizhny Novgorod, Russia
3Space Research Institute, RAS, Moscow, Russia
4Sodankylä Geophysical Observatory, Sodankylä, Finland
5Department of Space Physics, Institute of Atmospheric Physics of the Czech Academy of Sciences, Prague, Czechia
6Faculty of Mathematics and Physics, Charles University, Prague, Czechia
Format: article
Version: published version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2020052939702
Language: English
Published: American Geophysical Union, 2020
Publish Date: 2020-10-27
Description:

Abstract

We study quasiperiodic very low frequency (VLF) emissions observed simultaneously by Van Allen Probes spacecraft and Kannuslehto and Lovozero ground‐based stations on 25 December 2015. Both Van Allen Probes A and B detected quasiperiodic emissions, probably originated from a common source, and observed on the ground. In order to locate possible regions of wave generation, we analyze wave‐normal angles with respect to the geomagnetic field, Poynting flux direction, and cyclotron instability growth rate calculated by using the measured phase space density of energetic electrons. We demonstrate that even parallel wave propagation and proper (downward) Poynting flux direction are not sufficient for claiming observations to be in the source region. Agreement between the growth rate and emission bands was obtained for a restricted part of Van Allen Probe A trajectory corresponding to localized enhancement of plasma density with scale of 700 km. We employ spacecraft density data to build a model plasma profile and to calculate ray trajectories from the point of wave detection in space to the ionosphere and examine the possibility of their propagation toward the ground. For the considered event, the wave could propagate toward the ground in the geomagnetic flux tube with enhanced plasma density, which ensured ducted propagation. The region of wave exit was confirmed by the analysis of wave propagation direction at the ground detection point.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 125
Issue: 5
Article number: e2020JA027776
DOI: 10.1029/2020JA027776
OADOI: https://oadoi.org/10.1029/2020JA027776
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
114 Physical sciences
111 Mathematics
Subjects:
Funding: Comparison of spacecraft and ground-based data and modeling (A. D., L. T., D. P., A. L., and A. N.) was supported by the Russian Science Foundation (Project 15–12–20005). The work on the ground-based data was supported by the Academy of Finland under Grant 315716. The work of O. S. was supported by MSMT CR through the LTAUSA17070 project and by the Praemium Academiae Award from The Czech Academy of Sciences.
Academy of Finland Grant Number: 315716
Detailed Information: 315716 (Academy of Finland Funding decision)
Copyright information: © 2020. American Geophysical Union.