Propagation of lower-band whistler-mode waves in the outer Van Allen belt: Systematic analysis of 11 years of multi-component data from the Cluster spacecraft

O. Santolík , E. Macusova , Ivana Kolmasova , Nicole Cornilleau-Wehrlin (1, 2) , Y. Conchy (2)

1 LPP - Laboratoire de Physique des Plasmas
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique

Lower-band whistler-mode emissions can influence the dynamics of the outer Van Allen radiation belts. We use 11 years of measurements of the STAFF-SA instruments onboard the four Cluster spacecraft to systematically build maps of wave propagation parameters as a function of position. We determine probability distributions of wave vector angle weighted by the wave intensity. The results show that wave vector directions of intense waves are close to a Gaussian-shaped peak centered on the local magnetic field line. The width of this peak is between 10 and 20 degrees. The cumulative percentage of oblique waves is below 10–15%. This result is especially significant for an important class of whistler-mode emissions of lower-band chorus at higher latitudes, well outside their source region, where a simple ray tracing model fails and another mechanism is necessary to keep the wave vectors close to the field-aligned direction.

Domaines: Physique des plasmas [physics.plasm-ph]; Astrophysique [astro-ph]; Planète et Univers [physics]

O. Santolík, E. Macusova, Ivana Kolmasova, Nicole Cornilleau-Wehrlin, Y. Conchy. Propagation of lower-band whistler-mode waves in the outer Van Allen belt: Systematic analysis of 11 years of multi-component data from the Cluster spacecraft. Geophysical Research Letters, 2014, 41, pp.2729-2737. ⟨10.1002/2014GL059815⟩. ⟨hal-01552026⟩