Abstract

Kawai et al. (2021) reported the first ground-satellite conjugate observation of nighttime medium-scale traveling ionospheric disturbances (MSTIDs), by analyzing measurements from an airglow imager at Gakona (geographic latitude: 62.39°N, geographic longitude: 214.78°E, magnetic latitude: 63.60°N) and the Arase satellite in the magnetosphere on 3 November 2018. The Arase satellite observed variations in both the polarization electric field and the electron density as the Arase footprint passed through the MSTID structures in the ionosphere. In this study, we investigated whether these electric field and density variations associated with MSTIDs at subauroral latitudes are always observed by Arase in the magnetosphere. We used three airglow imagers installed at Gakona, Athabasca (geographic latitude: 54.60°N, geographic longitude: 246.36°E, magnetic latitude: 61.10°N), and Kapuskasing (geographic latitude: 49.39°N, geographic longitude: 277.81°E, magnetic latitude: 58.70°N) and the Arase satellite. We found eight observations of MSTIDs conjugate with Arase. They indicate that electric field and density variations associated with MSTIDs are not always observed in the magnetosphere. These variations tend to be observed in the magnetosphere during geomagnetically quiet times and when the amplitude of the MSTID is large. We categorized the MSTIDs into those caused by plasma instabilities and gravity waves and found that the electric field and density variations can be observed in the magnetosphere for both types of MSTIDs.