2024 Workshop: Quiet Ionsopshere

While geomagnetic storm time variations have consumed all the attention of the past studies of the ionosphere-thermosphere (IT) and the storms are clearly defined (e.g. a rapid decrease followed by a slow recovery in Dst index), the quiet state IT system has largely been neglected and is more challenging to study. “Quiet state” IT system is widely used as the reference state when investigating the IT under various conditions. However, the quiet geomagnetic activity is not clearly defined and thus could have resulted in biased understanding of the IT system. Can we say that in the absence of geomagnetic disturbances, the IT system is quiet? Can we really use the widely used geomagnetic indices, such as a low Kp, as a criterion of no geomagnetic activities? We have noticed that there are cases that low Kp and AE indices are no guarantee of absence of geomagnetic activities that are revealed by other observations. Perhaps, a long duration of the IMF Bz northward condition or low solar wind and magnetosphere coupling rate can give us a peace of mind, but then the question becomes how long the duration should be then we can assure the IT system is quiet. We invite you to join the discussion of the IT system under low Kp and AE index yet not absent of the geomagnetic activities and the true definition of quiet state of the IT system. Having a better definition and understanding of the quiet state will be of great help to investigate the long-term trend and ionospheric impact from atmospheric input. New observations and model simulations are welcomed.