[P-EM15] Study of coupling processes in solar-terrestrial system

[PEM15-P05] Study of ionospheric E-F region coupling by the long-term MU radar observation

*Tatsuhiro Yokoyama¹, Rei Morishita¹, Mamoru Yamamoto¹ (1.Research Institute for Sustainable Humanosphere, Kyoto University)

Keywords:MU radar, Field-aligned irregularities, E-F region coupling

Field Aligned Irregularities(FAI) is one of the plasma instability phenomena that occur in the ionospheric E and F regions. It is a phenomenon in which plasma density perturbation grows in the direction perpendicular to the magnetic field lines. The MU radar, a large atmospheric radar, has been used to observe FAI for several decades. By pointing the radar beam in the direction orthogonal to the magnetic field lines, coherent backscatter echoes can be received. In this study, we performed a statistical analysis of the long-term FAI observations by the MU radar from 1986 to 2013.
The simultaneous observations show that the occurrence of F-region FAI was preceded by E-region FAI in the most cases, although there were some cases where F-region FAI preceded. This result is consistent with the E-F region coupling theory, in which the electric field in the E region strengthens the instability growth in the F region. In addition, we used GPS-TEC data to survey the correlation between the occurrence of FAI and the occurrence of MSTID. As a result, among 70 days when FAI echoes were observed in both the E and F regions, MSTID was also observed on 69 days. This suggests that the coupling process is also important for MSTID generation as well as F-region FAI, which is also consistent with previous studies.