Chorus-related electrostatic bursts in the Earth's outer magnetosphere

We report here recent studies of wideband plasma wave data from the ISEE 1 and ISEE 2 spacecraft which reveal that whistler-mode chorus emissions in the Earth's outer magnetosphere are often accompanied by high-frequency bursts of electrostatic noise. The chorus features that correlate to the electrostatic bursts have a hook-like frequency-time variation in the frequency range 200-400 Hz, and the associated electrostatic bursts have a frequency range of ∼4-8 kHz. In some cases these electrostatic bursts have a harmonic frequency structure with a frequency spacing corresponding to the chorus frequency. This harmonic structure apparently results from the fact that the burst intensity is modulated at the chorus frequency.