University of Oulu

Bezděková, B., Němec, F., Manninen, J., Hospodarsky, G. B., Santolík, O., Kurth, W. S., & Hartley, D. P. (2020). Conjugate observations of quasiperiodic emissions by the Van Allen Probes spacecraft and ground‐based station Kannuslehto. Journal of Geophysical Research: Space Physics, 125, e2020JA027793.

Conjugate observations of quasiperiodic emissions by the Van Allen Probes spacecraft and ground‐based station Kannuslehto

Saved in:
Author: Bezděková, B.1; Němec, F.1; Manninen, J.2;
Organizations: 1Faculty ofMathematics and Physics, Charles University, Prague, Czech Republic
2Sodankylä Geophysical Observatory, Sodankylä, Finland
3Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA
4Department of Space Physics, Institute of Atmospheric Physics, The Czech Academy of Sciences, Prague, Czech Republic
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.5 MB)
Persistent link:
Language: English
Published: American Geophysical Union, 2020
Publish Date: 2021-02-16


Whistler mode waves observed in the Earth’s inner magnetosphere at frequencies between about 0.5 and 4 kHz which exhibit a nearly periodic time modulation of the wave intensity are called quasiperiodic (QP) emissions. Conjugate measurements of QP events at several different locations can be used to estimate their spatial extent and spatiotemporal variability. Results obtained using conjugate QP measurements provided by the ground‐based station Kannuslehto (L≈5.5) and the Van Allen Probes spacecraft (L shells between about 1.1 and 6.5) between September 2012 and November 2017 are presented. Altogether, 26 simultaneously detected events were analyzed. The event modulation periods and frequency‐time structures were generally the same at all observation points. Spatial separations of the spacecraft and the ground‐based station during conjugate observations are typically within about 40° in azimuth and from about 1 to 3 in L shell. RBSP consistently observes events at lower L shells than Kannuslehto, with the event occurrence primarily inside of the plasmasphere. Ratios of Poynting fluxes observed by the spacecraft and on the ground are used to evaluate event intensity variations related to the spacecraft position. It is found that the intensity decreases considerably both at low L shells and outside of the plasmasphere. Finally, an event containing a gap in its frequency‐time structure related to a sudden change of its properties is analyzed in detail.

see all

Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 125
Issue: 6
Article number: e2020JA027793
DOI: 10.1029/2020JA027793
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
114 Physical sciences
Funding: The work of B. B., F. N., and O. S. was supported by the GAČR Grant 18‐00844S and by MŠMT Grant LTAUSA17070. The work of O. S. was further supported by the Premium Academiae award from the CAS. The work at the University of Iowa was performed under the support of JHU/APL Contract 921647 under NASA Prime Contract NAS5‐01072.
Dataset Reference: The EMFISIS data as well as the list of plasmapause crossings are available at The list of Kannuslehto campaigns and quick look plots of measured frequency‐time spectrograms are available at
Copyright information: © 2020. American Geophysical Union.