Journal article
Conjugate Observations of Quasiperiodic Emissions by the Van Allen Probes Spacecraft and Ground-based Station Kannuslehto
Journal of geophysical research. Space physics, Vol.125(6), e2020JA027793
06/01/2020
DOI: 10.1029/2020JA027793
Abstract
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 approximate to 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 degrees 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.
Details
- Title: Subtitle
- Conjugate Observations of Quasiperiodic Emissions by the Van Allen Probes Spacecraft and Ground-based Station Kannuslehto
- Creators
- B. Bezdekova - Charles UniversityF. Nemec - Charles UniversityJ. Manninen - Sodankyla Geophys Observ, Sodankyla, FinlandG. B. Hospodarsky - University of IowaO. Santolik - Charles UniversityW. S. Kurth - University of IowaD. P. Hartley - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.125(6), e2020JA027793
- Publisher
- Amer Geophysical Union
- DOI
- 10.1029/2020JA027793
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 13
- Grant note
- LTAUSA17070 / MSMT Grant 921647; NAS5-01072 / JHU/APL Contract under NASA 18-00844S / GAR Grant Premium Academiae award from the CAS
- Language
- English
- Date published
- 06/01/2020
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984455363202771
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