Observation of Cyclotron Waves Resonantly Excited under Electron Cyclotron Resonance Heating at Magnetic Beach

Frequency analyses are made for cyclotron radiations emitted from electrons under electron cyclotron heating in a magnetic beach. In addition to a broad spectrum due to incoherent emissions a new spectrum is observed that is attributed to coherent emissions from spatially bunched electrons triggered by velocity space modulation by ECH and enhanced by magnetic-mirror effect.