The recent cycle 23/24 solar minimum was unusually prolonged compared to the previous several minima, and it had the most days without sunspots since the 1933 minimum. Weaker forcing of the upper atmosphere by solar EUV irradiance seems to have contributed to substantial changes in the ionosphere-thermosphere system. Measurements indicate large departures from empirical models like MSIS and IRI during the years 2006–2009, and a full explanation of these anomalies has not yet emerged. On the other hand, the lack of solar variability during this minimum has made forcing from below (e.g., via planetary and tidal waves) more prominent, thus affording the opportunity to better understand coupling with the underlying atmosphere.
We welcome contributions that compare observations with model predictions during the recent minimum, provide explanations for the unusual ionosphere-thermosphere behaviour, or show comparisons with other solar minima. Also solicited are contributions dealing with the altered wave forcing of the ionosphere and thermosphere during low solar activity. Observational and modelling studies are both welcome.