Summary
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.
Whenever we detected unexpected variability in SWARM data we will statistically evaluate if the lower atmosphere might serve as a source region for these variabilities. Then, atmospheric waves may serve as an explanation. We will derive and analyze our well-established indices of planetary wave and gravity wave dynamics in the UMLT to characterize those waves and quantitatively estimate their contribution to the observed variability in the ionosphere. We evaluate, if the disturbances in the ionosphere during the quiet periods are causing less accurate outputs of the IRI-model, in such case we would provide the improved version of IRI model based on Swarm electron density data. We aim to deliver the typical quantities of the dynamics as a look up table to contribute to modeling of the baseline conditions. A better quantification of the role of UMLT wave dynamics in the occurrence of solar quiet ionospheric disturbances will be achieved along with abetter representation of baseline ionospheric conditions.
