[P-EM28_29PM1] 磁気圏-電離圏結合

[PEM28-08] 朝夕昼夜境界付近で観測されるPi 2型地磁気脈動の性質

*今城 峻¹、吉川 顕正²、魚住 禎司²、大谷 晋一³、中溝 葵⁴、Marshall Richard⁵、Shevtsov Boris M.⁶、Akulichev Victor A.⁷、Sukhbaatar Usnikh⁸、湯元 清文² (1.九州大学大学院理学府地球惑星科学専攻、2.九州大学国際宇宙天気科学・教育センター、3.ジョンホプキンス大学応用物理学研究所、4.FMI, Arctic Research Unit、5.IPS Radio and Space Services, Bureau of Meteorology, Australia、6.Institute of Cosmophysical Researches and Radio Wave Propagation、7.Pacific Oceanological Insititude, FEB RAS、8.The Research Center of Astronomy and Geophysics of Mongolian Academy of Sciences)

キーワード：Pi 2型地磁気脈動, 朝夕昼夜境界, 電離層電流, 沿磁力線電流

We statistically investigate low-latitude Pi 2 pulsations observed around the dawn and dusk terminator. The main observational results of this study are: (1) Pi 2 pulsations tended to have east-west polarity in the sunlit side of the dawn terminator, while these in the sunlit side of the dusk terminator tended to have north-south polarity. (2) Phase reversals of D-component oscillations occurred near the dawn terminator and 2-3 hours before the dusk terminator. (3) Peaks of D/H (maximum amplitude ratio between D and H component) appear 3 hours after the dawn terminator and near the dusk terminator.We suggest that there is the dawn-dusk asymmetry of meridional ionospheric currents connecting between equatorial Cowling current and oscillating nightside FACs; meridional currents around dawn is more intense than around dusk. This asymmetry current system can be qualitatively explained by the deformation of potential pattern caused by polarization charges at the terminator.