Generation mechanism of the whistler-mode waves in the plasma sheet prior to magnetic reconnection |
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Authors: | XH Wei JB Cao GC Zhou HS Fu O Santolík H Rème I Dandouras N Cornilleau A Fazakerley |
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Institution: | 1. State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, China;2. Beihang University, Beijing 100190, China;3. Institute of Atmospheric Physics of the Academy of Sciences of the Czech Republic, Charles University, Prague, Czech Republic;4. Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic;5. IRAP, University of Toulouse, UPS-OMP, Toulouse, France;6. CNRS, IRAP, 9 Ave. Colonel Roche, BP 44346, F-31028 Toulouse cedex 4, France;g CETP/UVSQ, Velizy, France;h Univ. College London, London, UK |
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Abstract: | The whistler-mode waves and electron temperature anisotropy play a key role prior to and during magnetic reconnection. On August 21, 2002, the Cluster spacecrafts encountered a quasi-collisionless magnetic reconnection event when they crossed the plasma sheet. Prior to the southward turning of magnetospheric magnetic field and high speed ion flow, the whistler-mode waves and positive electron temperature anisotropy are simultaneously observed. Theoretic analysis shows that the electrons with positive temperature anisotropy can excite the whistler-mode waves via cyclotron resonances. Using the data of particles and magnetic field, we estimated the whistler-mode wave growth rate and the ratio of whistler-mode growth rate to wave frequency. They are 0.0016fce (Electron cyclotron frequency) and 0.0086fce, respectively. Therefore the whistler-mode waves can grow quickly in the current sheet. The combined observations of energetic electron beams and waves show that after the southward turning of magnetic field, energetic electrons in the reconnection process are accelerated by the whistler-mode waves. |
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Keywords: | Whistler-mode waves Electron temperature anisotropy Reconnection The plasma sheet |
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