[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-06] F-region depletion in the polar cap ionosphere under quiet geomagnetic conditions

*Khan-Hyuk Kim¹、Dong-Hee Kim¹、Hyuck-Jin Kwon²、Geonhwa Jee²、Young-Bae Ham²、Changsup Lee²、Jeong-Han Kim² (1.School of Space Research, Kyung Hee University、2.Korea Polar Research Institute)

キーワード：F-region ionosphere, Polar cap, Polar hole

F-region electron density depletion observed in the winter/nighttime polar cap ionosphere during solar minimum is studied using measurements made from VIPIR/Dynasonde at Jang Bogo Station (JBS), located at Terra Nova Bay in Northern Victoria Land in Antarctica (geographic: 74.62°S, 164.22°E/AACGM geomagnetic: 79.9°S, 53.6°W). We focus on F-region depletion (known as polar hole) events following a steady quiet condition, which is defined with Kp values < 1+ during 6 h. 45 polar holes were identified by JBS VIPIR/Dynasonde in 2019. All of the events started over a wide range of nightside magnetic local time (MLT = 19-03 hr) with a peak occurrence at MLT = 22-24 hr. They ended in a range of MLT = 20-06 hr, and ~82% of them (37 out of 45) ended before 03 MLT, implying that there is a great chance of detecting a polar hole event on the nightside MLT region. The polar hole events last one to five hours. In this study we discuss the role of plasma convection in the formation of the polar holes.