Evaluating the effects of the Earth's foreshock configurations on the "quiet-time" ionosphere

The day-to day variability of quiet-time ionosphere is surprisingly high even during periods of negligible solar forcing. Relatively well understood is the high-latitude variability where the solar wind is directly driving the high latitude currents, convection electric field or polar aurorae. But the current
understanding does not allow to accurately model the ionospheric state during the quiet-time conditions at mid- and low-latitudes. Surprising effects remain even at mid-latitudes, including for instance double daily maxima of ionospheric critical frequency.
European Space Agency's SWARM satellite constellation measurements allow the characterization of the upper atmospheric conditions and dynamics for already more than 10 years. The analysis of SWARM electron density and electric field data already showed that the ionosphere at mid-latitudes shows a non-negligible variability without a-priori solar driver, during negligible variations both in X-ray/EUV fluxes and missing disturbances in the solar wind. This often significant ionospheric variability currently remains unexplained, and further studies need to evaluate contributions by couplings from below comparing with those from above, i.e. checking the frequencies matching the foreshock waves with the local field-line resonances.

After efforts to properly select such "solar-quiet" periods, we compare the SWARM-detected variability trying to relate them to observations of magnetospheric ULF waves and configurations of the Earth foreshock mainly infered from the NASA's THEMIS satellite fleet and Wind solar wind observations.