HIGH-RESOLUTION RADAR OBSERVATIONS OF DAYTIME KILOMETER-SCALE WAVE STRUCTURE IN THE EQUATORIAL ELECTROJET

Using a new antenna configuration and new data processing hardware, we probed the electrojet with unprecedented spatial resolution in Januar y 1991 at Jicamarca. The altitude resolution was 125 m, and the east-w est antenna beamwidth was about 0.6 degrees, or about 1 km at electroj et altitudes. The high spatial resolution allowed us to observe, at ce rtain altitudes and times, pronounced wavelike structures with vertica l wavelengths of the order of 1 km and periods of tens of seconds. The se observations closely resemble the predictions of recent nonlocal, n onlinear numerical simulations of large-scale turbulence in the equato rial electrojet (Ronchi et al., 1991). The comparison demonstrated the validity of the theory and confirmed the idea that the Doppler power spectra of type 2 echoes at 50 MHz (due to 3-m plasma waves generated by the gradient-drift instability and a nonlinear cascade of energy fr om long-wavelength modes to short) are controlled primarily by the lar ge-scale dynamics and not by the nonlinear local growth and decay rate s of the 3-m waves themselves.