Comparisons of Auroral Hiss Spectra Observed at Syowa and Mizuho Stations (c. Wave-Particle Interactions in the Magnetosphere) (Proceedings of the Second Symposium on Coordinated Observations of the Ionosphere and Magnetosphere in the Polar Regions : Part I)

Simultaneous observations of auroral hiss emissions have been carried out at Syowa and Mizuho Stations. The intensity of auroral hiss emissions was different from case by case at the two stations. However the spectral shapes of hiss emissions obtained at both stations were generally similar and the delay of the occurrence time of auroral hiss between the two stations can not be recoanized within one second accuracy. These results show that the observable scale of the similar auroral hiss on the ground is wider than the distance between Syowa and Mizuho Stations (～270 km). From the examinations of the auroral photographs observed on the DMSP satellite and the auroral hiss emissions observed on the ground, when the aurora is located farther than 600 km from the station, hiss emissions are not observed at the station reducing the threshold level (～10^<-16> W/m^2Hz), These results suggest that the maximum observable region is within about 600 km. The ray-tracing result shows that 8 kHz hiss waves departed from the duct at altitude of 3000 km on the geomagnetic field line of λ=700°spread over the around in scale of 300 km. This calculation result is consistent with our observation results.