A statistical study of the propagation characteristics of whistler waves observed by Cluster
Article first published online: 19 OCT 2011
Copyright 2011 by the American Geophysical Union.
Geophysical Research Letters
Volume 38, Issue 20, October 2011
How to Cite
2011), A statistical study of the propagation characteristics of whistler waves observed by Cluster, Geophys. Res. Lett., 38, L20103, doi:10.1029/2011GL049597., , , and (
- Issue published online: 19 OCT 2011
- Article first published online: 19 OCT 2011
- Manuscript Revised: 16 SEP 2011
- Manuscript Accepted: 16 SEP 2011
- Manuscript Received: 7 SEP 2011
Vol. 39, Issue 24, Article first published online: 29 DEC 2012
- VLF/ELF waves;
- radiation belts
 VLF waves play a crucial role in the dynamics of radiation belts, and are responsible for the loss and the acceleration of energetic electrons. Modeling wave-particle interactions requires the best possible knowledge for how wave energy and wave-normal directions are distributed in L-shells and for the magnetic latitudes of different magnetic activity conditions. In this work, we performed a statistical study for VLF emissions using a whistler frequency range for nine years (2001–2009) of Cluster measurements. We utilized data from the STAFF-SA experiment, which spans the frequency range from 8.8 Hz to 3.56 kHz. We show that the wave energy distribution has two maxima around L ∼ 4.5 − 6 and L ∼ 2, and that wave-normals are directed approximately along the magnetic field in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude, and so that at latitudes of ∼30°, wave-normals become nearly perpendicular to the magnetic field. The observed angular distribution is significantly different from Gaussian and the width of the distribution increases with latitude. Since the resonance condition for wave-particle interactions depends on the wave normal orientation, our results indicate that, due to the observed change in the wave-normal direction with latitude, the most efficient particle diffusion due to wave-particle interaction should occur in a limited region surrounding the geomagnetic equator.