New observations from the FAST satellite demonstrate strong wave‐particle interactions between energetic electrons and H+ EMIC waves in inverted‐V arcs. The intense waves are shown to occur in strong upward current regions which contain intense downgoing field‐aligned electron fluxes. Electrons near the inverted‐V spectral peak have large, factor of 2 to 10, coherent flux modulations at or near the wave frequency. The electron modulations are typically centered at about fCH+/2 where fCH+ is the local H+ cyclotron frequency. The EMIC waves are broadbanded, extending from about 0.3fCH+ to 0.7fCH+. These waves also accelerate cold secondary electrons, forming counterstreaming field‐aligned electrons at energies up to about 300 eV. In addition, electron modulations at fCH+ are observed in the density cavities associated with upgoing ion beams. Intense waves at fCH+ are simultaneously detected and shown to have a magnetic component similar to the EMIC waves.
