[P-EM11] Coupling Processes in the Atmosphere-Ionosphere System

[PEM11-P03] Imaging observation of Ionospheric Field Aligned Irregularities by the PANSY radar at Antarctic Syowa Station

*Daisuke Kagawa¹, Taishi Hashimoto², Akinori Saito¹, Koji Nishimura², Masaki Tsutsumi², Toru Sato³, Kaoru Sato⁴ (1.Graduate School of Science, Kyoto University, 2.National Institute of Polar Research, 3.Graduate School of Informatics, Kyoto University, 4.Graduate School of Science, Tokyo University)

Keywords:PANSY radar, Field Aligned Irregularities, CLEAN, QP echoes, Pc5 pulsation

Program of the Antarctic Syowa Mesosphere-Stratosphere-Troposphere/Incoherent Scatter (PANSY) radar is a large atmospheric and VHF-band radar located at the Antarctic Syowa Station. This radar has a 47 MHz frequency, so it is capable of observing the coherent echoes from 3-m-scale field aligned irregularities (FAIs) in E-region. In this study, we observed them using the PANSY radar, and estimated the 2-dimensional spatial distribution of FAI echoes by the radar imaging. However, the imaging using the Fourier or Capon methods suffers the "ghosts" and the uncertainty of estimating the spatial distribution of FAI because of the beam pattern of the FAI array. On the other hand, the CLEAN method has the capability of estimating the spatial distribution of FAI echoes by removing the its effect, because it iteratively subtracts a scaled beam pattern centered on the location of the significant point on the obtained image. In April and December 2017, E-region FAI observation was operated by the PANSY radar. FAI echoes were detected on 6 observations out of 8, and periodic fluctuations of the echo intensity were shown in all of them. Furthermore, they were classed in two patterns according to their range structure, wide one and narrow one. In wide range echoes, quasi-periodic (QP) patterns with about 7-minite-period were shown. Applying the CLEAN method to one period of the QP echoes, we found the change of the range of the QP-FAI echoes. It was also figure out that the FAIs have the wave front aligned about -60 degrees azimuth angle and propagate from about northeast to southwest with a velocity of about 260 m/s. Furthermore, comparing with data of ionospheric electron density, these FAIs were considered to be produced by gradient-drift instability which were driven by the increases of electron density in ionospheric E-region. On the other hand, we found out that the time variations of narrow range echoes are correlated with Pc5 pulsation comparing with data of the variations of magnetic field on the ground at the Syowa station. The Pc5 pulsation shows the vatiations of H-component and D-component, so the plasma instability is driven by the strong electrojet with east and north component, and these FAIs are considered to be produced. The CLEAN method also showed little movement of these FAIs.