Statistical Study of Doppler Velocity and Echo Power Around 75° Magnetic Latitude Obtained With the Syowa EAST HF Radar

Masaaki FUKUMOTO, Nozomu NISHITANI and Tadahiko OGAWA
Nagoya University, Japan
Natsuo SATO, Hisao YAMAGISHI and Akira Sessai YUKIMATU
National Institute of Polar Research, Japan

Statistical analyses were made using three physical parameters (echo power, Doppler velocity, and spectral width) derived from Doppler spectra obtained from the Syowa East HF radar. In order to eliminate the effect of E-region echoes and the range dependence of the echo power, we selected echoes for the range of 1000 to 1500 km, so that all the data points were located around 75° geomagnetic latitude. Positive correlation was found between the absolute values of the Doppler velocity and the echo power. This relationship can be interpreted in terms of the gradient-drift plasma instability that is the most probable cause for the generation of decameter-scale irregularities in the F region ionosphere. This correlation becomes poor in the afternoon and midnight sectors. Detailed analyses suggest that other instabilities such as the current-convective and velocity-shear instabilities are still operative. The effect of neutral winds on the correlation was also found.

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