Thermal Cavitons

Abstract

The formation of small scale striations observed in ionospheric heating experiments is explained in terms of electrostatic waves propagating across the magnetic field, generated by linear conversion on the local density gradient and trapped in the density depletions. Enhancement of the process is due to ohmic overheating of the depletions, resulting in decreased density there. The process is centered at the upper hybrid level. Further growth is predicted when the initial density depressions exceed a threshold which is calculated. Such a nonlinear threshold is shown to be associated with a certain hysteresis phenomenon which has been observed in experiments.