2011 SuperDARN Workshop
Comparison of ionospheric azimuthal Pc5 plasma oscillations with geomagnetic pulsations on the ground and in geostationary orbit
K. Sakaguchi (1), T. Nagatsuma (1), T. Obara (2), and O.A. Troshichev (3)
(1) National Institute of Information and Communications Technology (NICT), Koganei, Tokyo, Japan
(2) Japan Aerospace Exploration Agency (JAXA), Tsukuba, Ibaraki, Japan
(3) Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia
abstract. The oscillations of azimuthal Doppler velocity in the ionosphere that had been observed in 2007 with a westward beam No.3 of SuperDARN King Salmon radar were analyzed in this study for the Pc5 frequency range. The local time distributions of the ionospheric oscillations showed peculiar asymmetric characteristics, that is the occurrence rate is maximum at the pre-midnight sector. The echos of 30-40 % contained Pc5 velocity oscillations from dusk to midnight, whereas the echos observed from dawn to noon hardly contained the oscillations. These ionospheric Pc5 events were compared with magnetic fields variations on the ground of Pebek and King Salmon under the beam, and the ETS-8 satellite orbiting at almost conjugate longitude in geostationary orbit. As a result, we identified only a few events that magnetic fields behaved sinusoidal variations in agreements with ionospheric oscillations. After statistical spectral analysis, on the other hand, we found that there wer e positive correlation between integrated Pc5-range spectral power of velocity oscillations and geomagnetic pulsations on the ground and in geostationary orbit. These results indicate that azimuthal Pc5 plasma velocity oscillations observed by the radar affect ground and geostationary magnetic-field spectral power. However, the local time distributions of ionospheric Pc5 events were different from previously reported Pc5 geomagnetic pulsations on the ground and in the magnetosphere. We examined in addition, the relation between ionospheric Pc5 power and solar-wind parameter, and found no linkage with neither solar wind velocity nor pressure variation. Therefore, ionospheric azimuthal Pc5 oscillations might not monitor well-known type of toroidal MHD waves driven by solar wind change, and Pc5 power distributions obtained by radar observations provide different features from magnetic field observations.