Coordinated Ground-Satellite Observations of VLF Hiss Emissions at Syowa Station : Relationships between Hiss and Aurora

ISIS VLF data were received at Syowa Station, Antarctica in 1976. These data were compared with VLF and auroral data simultaneously observed on the around. In general, hiss and saucer emissions were succesively observed on ISIS 2, when ISIS 2 moved from the polar cap towards the low latitude. It is found that the geomagnetic field lines through a northernmost auroral arc are located between the occurrence regions of hiss and saucer emissions. It is also found that spectra of hiss emissions observed on the ground (Syowa) are not similar to those of VLF emissions observed in the region connected with field line at the satel-lite altitude, but are similar to those of VLF emissions observed near the same geomagnetlc latitude as that of Syowa Station. The result suggests that auroral hiss emissions do not propagate along the geomagnetic field lines from the statellite height (～1400 km) to the ground. The calculation by means of the ray theory suggests that hiss emissions propagate along a non-ducted path from the satellite height to the groun