YOSHIKAWA Akimasa Kyushu University Faculty of Sciences Research Associate, 大学院・理学研究院, 助手 (70284479)
KAWANO Hideaki Kyushu University, Faculty of Sciences, Associate Professor, 大学院・理学研究院, 助教授 (60304721)
IIJIMA Takeshi Kyushu University, Faculty of Sciences, Professor, 大学院・理学研究院, 教授 (70011624)
KIKUCHI Takashi Communication Research Laboratory Chief Researcher, 通信総合研究所, 上席研究官
ITONAGA Masahiro Yamaguchi University Faculty of Education Professor, 教育学部, 教授 (60213104)
A purpose of this study is to understand a large-scale electromagnetic penetration and propagation process in the atmospheric transition region (the region from 80 to 5-600 Km in the height where neutral and charged particles are mixed in) from the polar to equatorial regions. By using the solar wind and particle data from the WIND and ISTP satellites, we clarified the relationships between the temporal and spatial scales of disturbances in the solar wind and the large-scale electromagnetic disturbances that can penetrate even into the equatorial region on the ground. Especially, in term of the composite data analysis from the satellites and ground-based observations, we can theoretically understand the electromagnetic coupling process between the polar and equatorial regions, including the solar wind, magnetosphere, ionosphere, atmosphere and conductive earth.
(1) A study on a propagation of the transient response of the magnetosphere
In this study, by investigation of the characteristi
cs of the polarization of magnetic variations on the ground due to the SI-event, we cleared that magnetic variations in the polar region associated with SC/SI events could be interpreted only by a motion of the vortex currents generated in the polar ionosphere. The motion of the ionosphere vortex current includes the information of the deformation of the magnetopause. Therefore, the present results suggest a possibility of the monitoring for the transient response of the whole magnetosphere from ground magnetic variations.
(2) A study on a global propagation of the ULF pulsations
From analyses of magnetic data from the Circum-pan-Pacific Magnetometer Network (CPMN) stations, it can be concluded that Pi 2 magnetic pulsations observed on the ground consist of at least five components : (1) a bouncing mode of impulsive field-aligned current at the auroral latitude, (2) a substorm current wedge oscillation (3) a surface wave at the plasmapause, (4) a cavity-like oscillation in the inner magnetosphere, and (5) a transmission of the Pi 2 electric field from the nightside auroral latitude to the dayside equatorial region. The ground Pi 2 pulsations are an ensemble of these five modes, which show their own propagations (or timings) and spatial illuminations.
(3) A study on the disturbance of the electric field in the ionosphere
In order to investigate the electric disturbances in the ionosphere, we installed the FM/CW radar at SASAGURI (Fukuoka City), and made steady observation of the variations of the ionosphere. As a result, we could successfully detect the temporal and spatial variations of the ionosphere due to the imposed electric field on the polar ionosphere. These observations reveal that the electric field imposed on the polar ionosphere spread event to the equatorial region almost simultaneously. Less