detected at Syowa Station, Antarctica, by means of differential-Doppler measurements of the 150 and 400 MHz beacon waves from six NNSS satellites. It is found from statistical analysis that (1) the medium-scale TID's at high-latitudes appear quite often during geomagnetically quiet and moderately disturbed conditions, and their occurrence seems not to increase with increasing geomagnetic activity, (2) they attain the maximum activity in winter and the minimum in summer, (3) diurnal variation shows the maximum occurrence around 1400-1600 LT with a second maximum around midnight, and (4) most of the medium-scale TID's propagate from south toward the cquator. These findings are compared with TID observations using NNSS
Impulsive plasma waves with a frequency range of 1–9 kHz were found in the wide‐band electric field data (650 Hz to 10 kHz) from the DE 1 satellite received at the Kashima station in Japan. The impulsive plasma waves were often accompanied by a strong hiss band at about 1 kHz, but not by a chorus. The frequency‐time spectra of these waves are very similar to those of electrostatic bursts associated with ELF chorus in the outer dayside magnetosphere, but these impulsive waves were observed at low geomagnetic latitudes in nightside magnetospheric regions much nearer the Earth for geomagnetic quiet and disturbed times. Local plasma densities (∼1 cm−3) obtained from the characteristic frequency of VLF emissions associated with the impulsive plasma waves agree with those observed simultaneously by the DE 1 retarding ion mass spectrometer. It is inferred from the local plasma density and the empirical relation of the plasmapause position with Kp that the impulsive plasma waves are occurring just outside the plasmapause. The impulsive plasma waves are discussed in terms of a resistive medium instability caused by Landau resonant trapping of thermal electrons by the associated hiss band at about 1 kHz, since this mechanism seems to be plausible from the available data and the frequency‐time spectra are similar to electrostatic bursts identified previously. Some of the events do not seem to have a strong ELF hiss band accompanying the impulsive plasma waves. It is suggested that these events may be due to electrons bunched by an ELF hiss band in a nearby region or may be caused by space discharges in the vicinity of the long‐wire antenna on the DE 1 spacecraft.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.