Sub-Auroral Plasma Turbulence in the E-Region Ionosphere: Microprocesses that Have Large Consequences on the Entire Geospace Environment

During periods of intense geomagnetic activity, the subauroral geospace region generates strong DC electric fields mostly orthogonal to the geomagnetic field. Electric fields mapped down magnetic field lines to the E-region ionosphere create there strong currents called electrojets. These drive mostly the Farley-Buneman, or modified two-stream, instability, though some other instabilities also contribute. These instabilities give rise to plasma turbulence that induces nonlinear particle transport and strong anomalous electron heating that elevates the temperature by up to one order of magnitude --- an effect that observed by radars for almost forty years. All these effects play an important role in magnetosphere-ionosphere coupling by increasing the ionospheric conductances and modifying the global energy flow. This will affect the entire behavior of the near-Earth geospace. A quantitative understanding of anomalous conductance and global energy transfer is important for accurate modeling of the space weather. For example, our theoretical analysis supported by 3D fully kinetic particle-in-cell simulations shows that during strong geomagnetic storms the inclusion of anomalous conductivity can more than double the total Pedersen conductance -- the crucial factor responsible for magnetosphere-ionosphere coupling through the current closure. These anomalous factors have already been included in a global magnetosphere-ionosphere-thermosphere modeling and have demonstrated their importance for accurate modeling of the near-Earth environment during big storms. They should also be taken into account when analyzing the sub-auroral geospace.

Work is supported by NSF Grants 1755350, 1500439 and NASA Grant 80NSSC19K0080.