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 also at mid- and low-latitudes. Surprising effects remains even at mid-latitudes, including for instance double daily maxima of ionospheric critical frequency.
Swarm measurements allow the characterization of the upper atmospheric conditions and dynamics (80-400 km) for more than 10 years now. The analysis of Swarm data also showed that the ionosphere is sometimes disturbed even during “quiet” solar periods: the electron density and electric field, for instance, can show significant variability that currently remains unexplained.Using Swarm data, supported by
extensive ground-based measurements of both, the upper mesospheric/ lower thermosphere (UMLT) and ionospheric D-, E- and F-region, as well as the International Reference Ionosphere Model (IRI), we contribute to characterize the atmospheric state during these quiet periods. Thus, QUID-REGIS contributes to the understanding of disturbances in the upper atmosphere and clarifies whether these are at least in parts a result of neutral atmospheric dynamics from the lower atmosphere at mid-latitudes. During solar quiet periods, we will analyze Swarm data to detect unexpected variability. For these periods, we will investigate measurements at lower heights for atmospheric variability. These measurements comprise
airglow observations representative for the neutral atmosphere in the UMLT (80-100km),
magnetic field (and other) observations representative for the ionospheric dynamo region (85-200km) as well as airglow observations from 200-300km altitude.
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