ELECTROSTATIC SOLITARY STRUCTURES IN NONTHERMAL PLASMAS

Solitary electrostatic structures involving density depletions have been observed in the upper ionosphere by the Freja satellite [Dovner el al., 1994]. If these are interpreted as ion sound solitons, the difficulty arises that the standard Korteweg-de Vries description predicts structures with enhanced rather than depleted density, Here we show that the presence of nea-thermal electrons may change the nature of ion sound solitary structures and allow the existence of structures very like those observed.