Thermal-driven cross-field plasma instabilities in the collision-dominated E-region ionosphere and Solar chromosphere: theory and simulations*

Electron thermal-driven (ET) plasma instability in the weakly ionized, collision-dominated plasma of the lower ionosphere have been predicted theoretically more than twenty years ago with some compelling observational evidence. A similar instability for the ionospheric ions (the IT instability) has also been  suggested. Similar to other known instabilities, such as the Farley-Buneman (FB) and gradient drift  instabilities, the ET and IT instabilities result in generating plasma density irregularities coupled to a turbulent electrostatic field. The underlying mechanism for both instabilities relates to ohmic heating of the plasma particles by a modulated electric field. The two thermal instabilities often co-exist with the FB instability, but the thermal mechanism allows explaining some features of the developed turbulence observed in fully kinetic particle-in-cell (PIC) simulations.  Recent PIC simulations for the Solar chromosphere parameters revealed ubiquitous instances of the developed ET instability under conditions when the FB instability was totally suppressed.  All this makes thermal instabilities a good candidate for laboratory modeling.