Electric fields during a substorm according to the CRRES satellite data

Two substorms with large impulsive electric fields measured on board the CR RES satellite at L similar to 6-6.5 are analyzed in this work. The accompan ying rapid local reconfiguration of the magnetic field testifies to an indu ctive nature of the observed E-field impulses with a duration of similar to 40 s and an intensity of >20 mV/m. When the satellite was near the plasma- sheet inner boundary, the field E had a predominant westward azimuthal comp onent at maximum. When the measurements were performed near the current-she et outer boundary, the predominant radial component of the impulsive field E was directed toward the Earth. In both cases, some initial disturbance of the fields E and B was observed 20-50 s before the local reconstruction of the held B. This was a simple increase in the field E and azimuthal curren t in the first case and field fluctuations with a period of similar to 50 s in the second case. The phase coupling between the E-y and B-z components corresponded to the even mode of standing hydromagnetic waves, which can be considered as coupled Alfven and slow magnetosonic waves. It is suggested that the initial disturbance, regardless of its origin, triggers a local no nlinear change in the B-field configuration.