Instabilities and formation of coherent structures

This tutorial paper is devoted to theoretical aspects of the coherent elect rostatic structures that have been encountered in various space plasmas. Th ese structures, called solitary waves, electrostatic shocks or double layer s have been observed in the solar wind, the Earth bow shock, the auroral zo nes and the magnetotail. Most of these structures can be interpreted in ter ms of electron or ion phase space holes. Their 1D structure, their emergenc e from plasma instabilities, their mutual interactions, their bidimensional stability, and their ability to create large scale electric fields are dis cussed in this paper.