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The negative impacts of space weather conditions on human activity have become a vital concern over the last decades, as humans increasingly use satellite communications, Positioning-Navigation-Timing (PNT) with Global Navigation Satellite Systems (GNSS), Earth’s observation and forecasting with in-situ and remote sensing satellites, and countless other applications. This situation underscores the necessity to better understand and predict the effects of Magnetosphere-Ionosphere-Thermosphere (MIT) processes and coupling in the near-Earth environment and to prevent potential detrimental influences on orbiting, aerial, and ground-based technologies (e.g., the radio signal propagation delay in the ionosphere affecting GNSS and communications, the drag force disturbances on Low Earth Orbit satellites, the power and internet outages due to intense electric currents induced during geomagnetic storms, etc.). For instance, the variability of the ozone layer has strong dependence on space weather, and it connects with the troposphere and the surface temperature variability. The ozone is a strong absorber of Solar ultraviolet (UV) and Earth’s long-wave radiations, playing thus a key role in global warming and climate change, which is affected by natural and human contributions such as solar activity and powerful ground-based radio transmitters. In the intricate MIT coupling, the UV and extreme UV (EUV) radiation are mostly absorbed by the thermosphere to create the ionosphere through ionization/dissociation of neutrals, and the thermosphere and ionosphere are strongly influenced by wave motions from the lower atmosphere, and also by energetic particle precipitation and field‐aligned currents through the magnetosphere and solar wind. Addressing the challenge of completely understanding the coupled MIT processes requires significant advances in geodetic observations of plasma and neutral density, “compositions”, and “velocities”, observations of energetic particles and “magnetic field perturbations” both in space and on the ground, as well as advanced theoretic and numerical modelling capabilities. The Joint Study Group 1 ‘Coupling processes between Magnetosphere, Ionosphere, and Thermosphere and (MIT)’ is implemented at the International Association of Geodesy (IAG) Inter-Commission Committee on Theory (ICCT), joint with the IAG Global Geodetic Observing System (GGOS), Focus Area on Geodetic Space Weather Research (FA-GSWR), the IAG Commission 4 ‘Positioning & Applications’, and the IAG Sub-Commission 4.3 ‘Atmosphere Remote Sensing’. The JSG1 aims to better understand Space Weather phenomena within the coupled MIT system, and formulate predictive models of the near-Earth space environment. We provide an introduction of the coupled MIT system and recent updates and results achieved by the group.

The magnetic field records of the magnetometer networks in the American, East Asian-Australian, and European-African sectors were employed in this present work. We used them to investigate equatorial electrojet (EEJ), counter electrojet (CEJ), tidal variability in EEJ strength and ionospheric current during the 2005/2006 and 2008/2009 sudden stratospheric warming (SSW) events. In addition to the well-investigated tidal variability in EEJ strength over the American and East Asian sectors, we investigated that of the African sector for the first time. Interestingly, the tidal components in EEJ strength during both SSW events clearly exhibit marked longitudinal differences with high, moderate, and low amplitudes in the American, East Asian, and African sectors, respectively. An exception found around day 71 in the African sector after the 2008/2009 SSW event had higher solar diurnal tidal component as compared to that of the Asian sector. Over the American sector, solar and lunar semidiurnal tides were strongly associated with CEJ current during both SSW events, whereas at the African and East Asian sectors such variabilities are not evident. A solar diurnal tidal component was strongly related to a reduction in the EEJ strength over the East Asian sector. In addition, a prolonged period of CEJ occurrence that begins during the SSW precondition and ends when the SSW was evolving characterized the African sector during both SSW events. There is a steady shift in phase at later hours when both SSW events are evolving.

In this study, the variations of topside ionospheric irregularities during 24 geomagnetic storms with Dst ≤ −50 nT in 2015 were examined through an algorithm specifically designed to detect a significant level of ionospheric irregularities. The algorithm was developed through the use of several parameters derived from the topside total electron content (TEC) observations from GRACE, Swarm-C, and Swarm-B. The local time characteristics of the observed equatorial plasma irregularities (EPIs) were analyzed during different phases of the storms, within 30° S–30° N magnetic latitudes. By comparing its results with corresponding in-situ electron density data and the results of previous studies, the algorithm was found to be efficient. It was observed that the detected EPIs at different stages of the storm showed local time dependence. For instance, EPIs were observed during nighttimes, but took place in the daytime occasionally during the storm main phase. Furthermore, the percentage occurrence rates were most prominent during the main phase at the post-sunset sector within less than 6 h of the storm onset. On the other hand, the occurrence rates became prominent in the post-midnight/morning sector during the recovery phase and even higher than observed in the post-sunset sector. Based on these findings it was concluded that the dominant driver of the enhanced EPIs during the post-midnight/daytime sector could be associated with disturbance dynamo electric fields.