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Short-periodic VLF emissions observed simultaneously by Van Allen Probes and on the ground
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  • Andrei G. Demekhov,
  • Elena E Titova,
  • Manninen Jyrki,
  • Alexander Nikitenko,
  • Sergey Vasilyevich Pilgaev
Andrei G. Demekhov
Institute of Applied Physics, Russian Academy of Sciences

Corresponding Author:andrei@ipfran.ru

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Elena E Titova
Polar Geophysical Institute
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Manninen Jyrki
Sodankyla Geophysical Observatory
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Alexander Nikitenko
Polar Geophysical Institute
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Sergey Vasilyevich Pilgaev
Polar Geophysical Institute
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Abstract

We present simultaneous observations of VLF emissions with periodic (2 or 4 s) bursts by Van Allen Probe near geomagnetic equator and Kannuslehto and Lovozero ground-based sites. The repetition period and ground–spacecraft delay are consistent with guided whistler wave propagation between conjugate ionospheres. In contrast to lightning whistlers, the group velocity dispersion is not accumulated from one burst to another, thus implying a nonlinear mechanism of its compensation. Two regimes are observed. In one regime, Poynting flux direction alternates in the magnetosphere, and the burst period is twice lower than on the ground, that corresponds to single wave packet bouncing along the field line. This regime is switched to the other one, with burst period unchanged in the magnetosphere but halved on the ground. In the second regime, no alternating Poynting flux direction is observed. This second regime corresponds to two symmetrically propagating wave packets synchronously meeting at the equator.