Waves at the electron plasma frequency in the magnetosheath
Abstract
Electrostatic plasma waves close to the electron plasma frequency are a typical feature of the foreshock region, but they are also less frequently observed in the magnetosheath. While the properties of foreshock waves, generated by electron beams reflected by the shock, have been studied for decades, the nature of high frequency magnetosheath waves has not been explored in detail. We used Cluster data to investigate the properties of such waves and compare their properties in the foreshock and magnetosheath. The fine structure of the waveform and the spectral shape of magnetosheath electrostatic waves is very similar to those observed in the foreshock and suggests an electron beam mode associated with unstable low energy electron beams. In the foreshock, Cluster consistently observes low energy electron beams associated with generation of the waves. Similar features, although less pronounced, are observed superimposed on the background flat-top magnetosheath electron distribution. Such waves were automatically identified in 9 years of Cluster magnetosheath crossings to analyze their spatial distribution and dependence on upstream solar wind and bow shock properties. The waves are observed more frequently close to the magnetopause and the weak dependence on upstream parameters suggests that the unstable distributions originate from magnetopause processes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMSH23D3363S
- Keywords:
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- 7827 Kinetic and MHD theory;
- SPACE PLASMA PHYSICSDE: 7829 Kinetic waves and instabilities;
- SPACE PLASMA PHYSICSDE: 7836 MHD waves and instabilities;
- SPACE PLASMA PHYSICSDE: 7894 Instruments and techniques;
- SPACE PLASMA PHYSICS