Simultaneous quasi-periodic optical and HF radar signatures observed in the postnoon sector

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Zhongshan Station in Antarctica is located close to the polar cusp/cleft latitude. The field of view of the Syowa East HF radar also covers Zhongshan Station. Simultaneous quasi-periodic phenomena of optical aurora, HF radar backscatter power and Doppler velocity, and ground based magnetograms were observed in the magnetic postnoon sector (〜330 MLT to 1510 MLT) on 3 August 1997. The characteristics of the quasi-periodic event are summarized in the following; 1) East-west aligned band/arc type discrete aurora showed quasi-periodic luminosity variations with period of -6-10 min, 2) Quasi-periodic variations of the optical aurora had one to one correspondence with the variations of HF radar backscatter powers and magnetic pulsations, 3) The HF backscatter region was located at the lower latitude of the quasi-periodic optical aurora, 4) Quasi-periodic variations of line-of-site Doppler velocity detected by HF radar showed very close relation to the magnetic pulsations observed at Zhongshan in Antarctica and the IMAGE magnetometer array in the northern hemisphere, 5) The IMAGE data revealed that the region of quasi-periodic HF radar backscatter (irregularities) corresponds to the region of intensity maximum of magnetic pulsations.
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