Identification of the source of quasiperiodic VLF emissions using ground-based and Van Allen Probes satellite observations

0465194 - ÚFA 2017 ZA eng A - Abstract
Demekhov, A. G. - Titova, E. E. - Kozelov, B. V. - Pasmanik, D. L. - Manninen, J. - Santolík, Ondřej - Kletzing, C. A. - Reeves, G.
Identification of the source of quasiperiodic VLF emissions using ground-based and Van Allen Probes satellite observations.
7th VERSIM-RBS: Abstracts. Hermanus: SANSA, 2016. s. 31.
[VERSIM and RadBelt 2016 /7./. 19.09.2016-24.09.2016, Hermanus]
Institutional support: RVO:68378289
Keywords : plasmasphere * Van Allen Probe A * whistler mode waves * quasiperiodic VLF emissions
Subject RIV: BL - Plasma and Gas Discharge Physics
https://events.sansa.org.za/images/2016/VERSIM/abstracts/VERSIM_2016_abstracts.pdf

We discuss quasiperiodic VLF emissions (in the frequency range 2 to 6 kHz) observed by
Van Allen Probe A and a ground based site in Kannuslehto (Finland, L = 5.5) during a
substorm of January 25, 2013. The spacecraft detected them in the night sector at L = 3.0
to 4.2 when it was in the plasmasphere. Their quasi-period decreased from 6 to 3 min
during the event. We find one-to-one correspondence between the quasiperiodic
elements detected in space and on the ground, which indicates the temporal nature of
the observed quasi-period variation.
Multiсomponent measurements of the wave electric and magnetic fields by the Van Allen
Probe A show that the quasiperiodic emissions were almost circularly right-hand
polarized whistler mode waves and had predominantly small (below 30°) wave vector
angles with respect to the magnetic field.
In the probable source region of these signals (L about 4), we observed synchronous
variations of electron distribution function at energies of 10–20 keV and the quasiperiodic
elements. In the pause between the quasiperiodic elements pitch angle distribution of
these electrons had a maximum near 90°, while they become more isotropic during the
quasiperiodic elements. The growth rate of whistler mode waves calculated for the
electron distribution functions measured by Van Allen Probe A corresponds well to the
spectra of observed emissions.
We propose to explain the quasiperiodic emissions by auto-oscillation regime of the
cyclotron instability and simulate such regimes using the flow cyclotron maser model for
the parameters close to measured ones.
Permanent Link: http://hdl.handle.net/11104/0263854