Plasma waves in the upstream and bow shock regions observed by GEOTAIL

Upstream waves in the foreshock of the Earth's bow shock are the manifestation of microscopic plasma dynamics caused by the solar wind interaction with the bow shock. Though the past wave observation has revealed many interesting features of the foreshock plasma waves, the lack of waveform observation could not provide sufficient information to understand the micro-physics of wave-particle interactions beyond certain points. The present paper describes the preliminary results of the GEOTAIL plasma wave observation in the upstream as well as in the bow shock regions. The waveform capture (WFC) receiver has revealed interesting waveforms in these regions which are to provide a clue of understanding the microphysics involved in the wave generation in the upstream and bow shocks. Based on the observed information, we classify the electron and ion foreshock regions into more detailed structures. We also have carried out some simple computer simulations to understand some of the observed wave phenomena.