STATISTICAL AND CASE-STUDIES OF RADIO EMISSIONS OBSERVED NEAR 2F(CE) AND 3F(CE) IN THE AURORAL-ZONE

Receivers located at Two Rivers, Alaska (64.9 degrees N, 146.9 degrees W), and Circle Hot Springs, Alaska (65.5 degrees N, 144.7 degrees W), have been used to monitor the spectrum between 0.05-4.8 MHz for exten ded periods. Seasonal and diurnal effects of auroral roar, a weak narr ow band radio emission near 2 and 3 times the ionospheric electron cyc lotron frequency (f(ce)), have been determined. Many individual aurora l roar events correlate with magnetic activity, and superposed epoch a nalysis using planetary K indices shows a correlation between magnetic activity and auroral roar commencement. For a 3f(ce) roar event on Ma rch 23, 1992, riometer, magnetometer, photometer, and all-sky camera d ata are available and show that individual bursts of 3f(ce) auroral ro ar are associated with intensifications of the aurora, as was known pr eviously for 2f(ce) roar. Finally, two possible generation mechanisms are investigated in detail: nonlinear interaction between lower hybrid and electrostatic upper hybrid waves producing electromagnetic waves, and the feasibility of a lower ionospheric decameter maser for direct generation of X mode waves at harmonics of f(ce).