SuperDARN Hokkaido Radar Observation of Recurrent Propagating SAID/SAPS Structure

The SuperDARN Hokkaido radar is the second mid-latitude SuperDARN radar, which started operation in November 2006. In this paper we study one event study of the recurrent propagating SAPS/SAID structure which was observed by the Hokkaido radar at 0830 - 0930 UT (1730 - 1830 MLT) on April 23, 2008. This period was during the main phase of a weak geomagnetic storm with minimum Dst about -37 nT. The IMF was southward and during this event it turned to northward. Its period, propagation velocity and wavelength are 30 min, 700 m/s and 1200 km respectively. It has similar characteristics to traditional ‘giant undulation' auroral structures although some of the parameters such as period are slightly different. Because of the unique location of the Hokkaido radar (geomagnetic latitude ~ 36.5 degrees), it is possible to cover the wide longitudinal extent of the SAPS / SAID structure at about 60 geomagnetic latitude. Possible generation mechanisms of these SAPS/SAID structures with recurrent / propagating characteristics will be discussed.