Dynamics of Ion Sound Waves in the Front of the Terrestrial Bow Shock
Abstract
Ion-sound turbulence played a crucial role in early models of anomalous processes in the shock front. Both the current and the gradient of electron temperature within the magnetic ramp region have been considered as sources of free energy for the ion sound instability in the shock front. Since the solar wind velocity upstream of the terrestrial bow shock usually exceeds the velocity of ion sound waves, these waves were expected to be observed in the region the ramp and downstream of it. However, the EFW instrument on board Cluster 3 measured ion sound wave packets in the upatream part of the foot region. These observations pose two questions, namely 'What is the generation mechanism of these waves?', and 'Why are ion sound waves observed as confined quasimonchromatic wave packets?'. The envelope of such wave packets results from nonlinearities in the wave dynamics. However, these nonlineararities do not appear in the solutions to the KdV equations which theoretically describe such wave packets. Internal burst mode data from the EFW instrument are used to separate spatial and temporal variations on a distance about 60 meters. Nonlinear frequency domain identification techniques have been applied to the observed ion sound waves. The results are used to identify possible wave sources and investigate their dynamics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMSH51D1708G
- Keywords:
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- 4490 NONLINEAR GEOPHYSICS / Turbulence;
- 7839 SPACE PLASMA PHYSICS / Nonlinear phenomena;
- 7851 SPACE PLASMA PHYSICS / Shock waves