Large-amplitude wave electric field in the inner magnetosphere during substorms

CRRES electric field data during substorms have been analyzed to investigate intense electric fields in the inner magnetosphere associated with dipolarizations. Substorm injections during 13:00-15:00 UT on 7 March 1991 exhibit many large-scale electric fields and short-duration electric field spikes. Large-scale electric fields with durations of ∼1 min are identified as spatial structures associated with the region 1 field-aligned currents. Amplitudes of electric fields reach 30 mV/m with a high correlation with variations of the magnetic field, and the Poynting fluxes are directed toward the ionosphere with magnitudes of more than 0.5 mW/m². 16-Hz high-resolution data show intense electric field spikes with amplitudes of ∼100 mV/m with durations of ∼1 s. Most of the spikes are electromagnetic with Poynting fluxes of ∼0.1 mW/m² directed toward the ionosphere. The electric field spikes are identified as right-handed whistler waves with a size of ∼1000 km with frequencies just below the ion cyclotron frequency. A nearly simultaneous measurement by the DMSP-F9 satellite shows intense plasma flows with durations of 1 s and inverted-V electron precipitation. An estimation of the wave and particle energy fluxes shows that about half of the Poynting flux of the electric field spikes is consumed accelerating auroral particles, and 1% of the Poynting flux drives the fast plasma flows at the ionosphere. It is suggested that the electromagnetic spikes provide sufficient energy for auroral particle acceleration.