References

ANGEO

Annales Geophysicae

ANGEO

Ann. Geophys.

1432-0576

Copernicus Publications

Göttingen, Germany

10.5194/angeo-26-699-2008

Lower hybrid waves at the shock front: a reassessment

Walker

S. N.

¹ Balikhin

M. A.

¹ Alleyne

H. St. C. K.

¹ Hobara

¹ André

² Dunlop

M. W.

Department of Automatic Control and systems Engineering, University of Sheffield, Sheffield, UK

Swedish Institute for Radio Physics-Uppsala Division, University of Uppsala, Sweden

Space Physics Division, SSTD, CCLRC Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK

26 03 2008

26 3 699 707

2008

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The primary process occurring at a collisionless shock is the redistribution of the bulk upstream energy into other degrees of freedom. One part of this process results in the acceleration of electrons at the shock front. Accelerated electrons are observed at the terrestrial and other planetary shocks, comets, and their effects are observed in astrophysical phenomena such as supernova remnants and jets in the form of X-ray bremsstrahlung radiation. One of the physical models for electron acceleration at supercritical shocks is based on low-hybrid turbulence due to the presence of reflected ions in the foot region. Since lower hybrid waves propagate almost perpendicular to the magnetic field they can be simultaneously in resonance with both the unmagnetised ions (ω=Vik⊥) and magnetised electrons (ω=Vek||). In this paper, Cluster observations of the electric field are used to study the occurrence of lower hybrid waves in the front of the terrestrial bow shock. It is shown that the lower hybrid waves exist as isolated wave packets. However, the very low level of the observed lower hybrid turbulence is too small to impart significant energisation to the electron population.

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