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

• Published in: Geophysical Research Letters
• Main Authors: Titova, E. E., Kozelov, B. V., Demekhov, A. G., Manninen, J., Santolík, O. (Ondřej), Kletzing, C. A., Reeves, G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: energetic electrons; quasiperiodic emissions; Van Allen Probes; VLF waves; Northern Finland
• Online Access: https://doi.org/10.1002/2015GL064911; http://hdl.handle.net/11104/0248933

We report on simultaneous spacecraft and ground-based observations of quasiperiodic VLF emissions and related energetic-electron dynamics. Quasiperiodic emissions in the frequency range 2-6kHz were observed during a substorm on 25 January 2013 by Van Allen Probe-A and a ground-based station in the Northern Finland. The spacecraft detected the VLF signals near the geomagnetic equator in the night sector at L=3.0-4.2 when it was inside the plasmasphere. During the satellite motion toward higher latitudes, the time interval between quasiperiodic elements decreased from 6min to 3min. We find one-to-one correspondence between the quasiperiodic elements detected by Van Allen Probe-A and on the ground, which indicates the temporal nature of the observed variation in the time interval between quasiperiodic elements. Multis{cyrillic}omponent 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.