On the frequency modulation of VLF emissions
The VLF-wave frequency modulation efficiency as a function of magnetosphere plasma parameters under the weak pitch-angle diffusion regime is studied. The study is based on the VLF growth-rate modulation both in the magnetosphere equatorial plane and after integrating along the magnetic field lin...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1996-11-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/14/1151/1996/angeo-14-1151-1996.pdf |
| Summary: | The VLF-wave frequency modulation efficiency
as a function of magnetosphere plasma parameters under the weak pitch-angle
diffusion regime is studied. The study is based on the VLF growth-rate
modulation both in the magnetosphere equatorial plane and after integrating
along the magnetic field line. It is shown that for the typical quiet
magnetosphere plasma parameters the relative shift of the maximum intensity
frequency <i>∆ω<sub>m</sub></i>/ω<i><sub>m</sub></i>
is approximately equal to relative disturbance of the magnetic field in the
magnetosphere equatorial plane, but may exceed it when both electron temperature
anisotropy and the parameter <i>αβ</i><sub>∥</sub>are
small; here α is the total-to-warm electron content ratio and
<i>β</i><sub>∥</sub> is the electron parallel beta. It is also shown
that relative shift of the maximum intensity frequency
<i>∆ω<sub>m</sub></i>/ω<i><sub>m</sub></i>
after integrating along the field line is not less than 50% from its value at
the equatorial plane, which allows the use of the equatorial-plasma-parameter
data to estimate the VLF frequency modulation on the ground. The upper cut-off
frequency modulation is considered as well. The calculated theoretical sonagrams
show that this frequency modulation may be related to the non-dispersive and to
the "inverted-V'' structures of QP hiss. |
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| ISSN: | 0992-7689 1432-0576 |