Electrostatic Auroral Density Cavities

A model set of nonlinear electrostatic equations is analyzed critically; they have been presented earlier to study the short-scale auroral density cavities (SSADC) observed by Freja satellite. It is shown that electron inertial effect is not necessary to obtain solitary structure through electrostatic nonlinear equations. The ion streaming and direction of propagation of the structure seem to be the two parameters that can decide the width of the density cavity.