Electrostatic Solitary Waves observed in the geomagnetic tail and other regions

The waveform capture receiver onboard the Geotail spacecraft has discovered Electrostatic Solitary Waves (ESW) as waveforms of the Broadband Electrostatic Noise (BEN) in the plasma sheet boundary layer. They mainly contribute to the high frequency parts of the broadband spectra. Several spacecraft before and after the Geotail observations have also reported similar solitary waveforms in other regions. They are observed in the polar magnetosphere, magnetosheath and bow shock regions. Some of them have not been discussed in relation to BEN. However, it is evident that their solitary waveforms contribute to broadband spectral structures in frequency space. In the present paper, we summarize the nature of the ESW observed by Geotail in the magnetotail region and discuss the generation mechanisms of solitary waves observed in other regions by comparing their properties.