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Rapid magnetic reconnection in the Earth’s magnetosphere mediated by whistler waves


Magnetic reconnection has a crucial role in a variety of plasma environments1,2,3 in providing a mechanism for the fast release of stored magnetic energy. During reconnection the plasma forms a ‘magnetic nozzle’, like the nozzle of a hose, and the rate is controlled by how fast plasma can flow out of the nozzle. But the traditional picture of reconnection has been unable to explain satisfactorily the short timescales associated with the energy release, because the flow is mediated by heavy ions with a slow resultant velocity. Recent theoretical work4,5,6 has suggested that the energy release is instead mediated by electrons in waves called ‘whistlers’, which move much faster for a given perturbation of the magnetic field because of their smaller mass. Moreover, the whistler velocity and associated plasma velocity both increase as the ‘nozzle’ becomes narrower. A narrower nozzle therefore no longer reduces the total plasma flow—the outflow is independent of the size of the nozzle. Here we report observations demonstrating that reconnection in the magnetosphere is driven by whistlers, in good agreement with the theoretical predictions.

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Figure 1: Collisionless reconnection configuration at dayside magnetopause for 10 January 1997.
Figure 2: Plasma and magnetic field data and dynamic frequency spectrogram of electric and magnetic fields observed by GEOTAIL PWI-MCA (Multi-Channel Analyzer) on transverses through the dayside magnetopause boundary on 10 January 1997.
Figure 3: High-resolution magnetic field data for GEOTAIL magnetopause crossing on 10 January 1997.


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We thank H. Kojima, J. F. Drake and R. R. Anderson for their help and valuable discussion, and T. Mukai and N. Nagai for providing the particle and magnetic field data, respectively. D.X.H. is on leave from Wuhan University and received support from the RASC Visiting Foreign Scientist programme. This work was supported by a Grant-in-Aid for Scientific Research.

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Correspondence to H. Matsumoto.

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Deng, X., Matsumoto, H. Rapid magnetic reconnection in the Earth’s magnetosphere mediated by whistler waves. Nature 410, 557–560 (2001).

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