Plasma wave instabilities may occur above discrete auroral arcs where the natural accelerated auroral electron component meets the cold ionospheric plasma. These wave-particle interactions were studied on the CAESAR II rocket by measuring the modulations in energetic electron flux in the frequency ranges 0--10 MHz and 0--10 kHz. Near apogee (700 km) a strong modulation of 7.5 keV electrons at 1.4 MHz (≈fUH) was observed where df(v)/dv was positive, just below the auroral beam velocity. The measurement is shown to be consistent with instabilities driven by both Landau and cyclotron resonant interactions with upper hybrid waves, and alsod with the earlier observation of modulatins at 2.65 MHz (≈fUH) seen on a low altitude rocket E2-B (apogee 230 km). ¿American Geophysical Union 1990