A case study of the spatial structure of the coherent Pc 3 pulsations

*Yoshimasa Tanaka[1] ,Kiyohumi Yumoto [1]
Tai-ichi Kitamura [1],S. I. Solovyev [2]
E. F. Vershinin [3]
Department of Earth and Planetary Siences, Kyushu University[1]
Institute of Cosmophysical Research and Aeronomy, Russia[2]
Institute of Cosmophysical Research and Radiowaves Propagation, Russia[3]

We analyzed the magnetic field data obtained simultaneously from the stations of the CPMN and the CANOPUS. In particular, the longitudinal spatial structure of Pc 3 pulsations at high latitude is focused. We selected the narrow-band Pc 3 events observed on June 3-4, 1995, which were coherent and nearly in-phase over a wide range of latitude (L=1.0 -8.6). As a result, we found some high coherence (>0.7) events even at the stations separated by 80 degrees in longitude. On the other hand, the spatial phase structure is not always in-phase or out-of-phase but more ambiguous, which does not support the ionospheric current model.

The spatial structure of the coherent Pc 3 pulsations has been studied statistically by using data from the Circum-pan Pacific Magnetometer Network (CPMN), which consists of the stations located along the 210 degrees magnetic meridian from the dip equator to polar region and the stations aligned to the magnetic equator. We obtained the ionospheric equivalent current system for the coherent Pc 3 pulsations, which has two vortices centered at 0700 LT and 1330 LT around 60 degrees in the magnetic latitude. However, since the spatial structure was acquired from the statistical study, a case study using data recorded simultaneously at the stations distributed globally is needed to confirm that the global current system is set up for each event.
We analyzed the magnetic field data obtained simultaneously from the stations of the CPMN and the CANOPUS. In particular, the longitudinal spatial structure of Pc 3 pulsations at high latitude is focused. The amplitude ratio, coherence, and phase difference were calculated by the fast Fourier transform (FFT) analysis. We selected the narrow-band Pc 3 events observed on June 3-4, 1995, which were coherent and nearly in-phase over a wide range of latitude (L=1.0-8.6). As a result, we found some high coherence (>0.7) events even at the stations separated by 80 degrees in longitude. On the other hand, the spatial phase structure is not always in- phase or out-of-phase but more ambiguous, which does not support the ionospheric current model. It is necessary to consider the propagation of the pulsations in the magnetosphere.