Interaction Between CME and Magnetosphere Observed by Cluster on Nov. 6, 2001: (1) Waves Excitation

Very few in situ measurements so far show the details of the interactions between CME and magnetosphere. Here we report a fortuitous observation that the Cluster spacecraft were located at the dusk-side magnetopause, meandering back and forth four times between the ICME and the magnetosphere, and observed part process of the interaction between the CME and the magnetosphere. The primarily analysis showed that: (1) a fast ion beam other than the ambient plasma was observed almost perpendicular to the magnetic field; (2) The left-hand-polarized kinetic Alfvén waves excitation by the ion beam; and (3) the resonances between the kinetic Alfvén waves and part of the beam particles lead to the pitch angle diffusion of resonant particles and formating of a monospheric distribution with nearly constant kinetic energy. The wave-particle resonance may pay an important role in the energy transfer and particle exchange across the magnetopause between the magnetosheath and magnetosphere during the CME impulsion.