Attempt to nowcast the latitudinal position of the SAPS structure using the SuperDARN Hokkaido Pair of radars

The Sub-Auroral Polarization Streams (SAPS) are one of the most outstanding phenomena in the subauroral ionosphere. Its position can be a measure for nowcasting the intensity/size of the global ionospheric convection. In the current study, the latitudinal distribution of SAPS is discussed based on the over ten years of observation achieved by the SuperDARN Hokkaido Pair of radars, which are located at the lowest geomagnetic latitudes among the SuperDARN radars. Previous statistical studies showed that the latitudinal position of the SAPS structure could be predicted on average as a function of magnetic local time and the Dst geomagnetic index. The multi-event study shows, however, that the latitude of the SAPS structure does not always follow the empirical relationship, which could determine the latitude of the SAPS structure as a function of the Dst index and magnetic local time. For example, a detailed analysis of the 8 Sep 2017 event indicates that the SAPS position is located at a significantly lower geomagnetic latitude than the statistically expected position, even if the magnetic local time and Dst geomagnetic activity effects are considered. Possible reasons for such an unusual position, including the history of the IMF and the solar wind parameters and occurrence of substorms, are investigated.