Statistical Study of Seasonal and Solar Activity Dependence of Nighttime MSTIDs Occurrence Using the SuperDARN Hokkaido Pair of Radars

We conduct a statistical analysis on nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) using the Super Dual Auroral Radar Network (SuperDARN) Hokkaido East (43.53°N, 143.61°E) high‐frequency (HF) radar data from 2009 to 2019 and the SuperDARN Hokkaido West (43.54°N, 143.61°E) HF radar data from 2016 to 2019. We analyze the line‐of‐sight Doppler velocity data, corresponding to the magnitude of the polarization electric field associated with nighttime MSTIDs. We find that the propagation direction of the nighttime MSTIDs is mainly southwestward and rotates clockwise with progressing local time. In addition, we identify a negative correlation between the nighttime MSTIDs amplitude and the solar F10.7 index. These tendencies can be explained by the Perkins instability, which is considered to be associated with the growth of nighttime MSTIDs. This study is the first to find the solar activity dependence of the polarization electric field fluctuations associated with the nighttime MSTIDs. Plain Language Summary Medium‐scale traveling ionospheric disturbances (MSTIDs) are propagating wave‐like electron density disturbances in the ionosphere. Previous studies have shown nighttime MSTIDs propagate mainly southwestward and the propagation direction changes clockwise with progressing local time at mid‐latitude. However, statistical studies using long‐term data are few in number, and long‐term trends, such as solar activity dependence, are still unknown. In this study, we report the results of statistical analysis on the characteristics of nighttime MSTIDs using long‐term data from the Super Dual Auroral Radar Network (SuperDARN) Hokkaido pair of radars. The nighttime MSTIDs in the northern region of Hokkaido have the same propagation characteristics with the MSTIDs in the other midlatitude region. In addition, the nighttime MSTID amplitude has a negative correlation with solar activity. Key Points Long‐term analysis on nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) was conducted using the SuperDARN Hokkaido pair of radars Seasonal and local time dependences were analyzed and these results were consistent with theoretical expectations of the Perkins instability Negative correlation between the MSTID amplitude and solar activity was found