Modulated Upper‐Hybrid Waves Coincident With Lower‐Hybrid Waves in the Cusp

Abstract During the Twin Rockets to Investigate Cusp Electrodynamics (TRICE‐2) High‐Flyer rocket's passage through cusp high frequency (HF) radio wave receiver observed three intervals of banded upper‐hybrid (UH) waves. The bands begin at UH ( 1.2–1.3 MHz), descending as low 1.1 MHz, with amplitudes hundreds mV/m. spacing are 4.5–6 kHz and number ranges from 3 10. Simultaneously, very (VLF) lower‐hybrid (LH) waves ranging 1 10 mV/m frequencies kHz. Slight variations spacings in were closely correlated LH peak frequencies. Two possible wave‐wave interactions explored explain this phenomenon: decay an into a lower wave, coalescence independent that spawn Using dispersion relation calculator electron ion distribution functions based off those by particle instruments suggests waves, lesser degree can be excited linear instabilities. Kinematic analysis relations matching conditions show linking modes either or coalescence. This along comparisons energy densities ratio their occupation numbers suggest process is more likely than