The 15 January 2022 eruption of the Hunga volcano provides a unique opportunity to study the reaction of the ionosphere to large explosive events. In particular, this event allows us to study the global propagation of travelling ionospheric disturbances using various instruments. We focus on the detection of the ionospheric disturbances caused by this eruption over Europe, where dense networks of both ionosondes and GNSS receivers are available. This event took place on the day of a geomagnetic storm. We show how data from different instruments and from different observatories can be combined to clearly distinguish the TIDs produced by the eruption from those caused by concurrent geomagnetic activity. By comparing observations obtained from multiple types of instruments, we also show that TIDs produced by various mechanisms are present simultaneously, with different types of waves affecting different physical quantities.

The ionospheric scale height is a key parameter that defines the shape of the electron density profile. Its main characteristic, including the diurnal variation and its altitudinal dependence are still under investigation. This paper analyses the characteristics of the effective scale height at middle latitudes based on coincident Digisonde and Swarm A satellite data. Based on the assumption that the topside electron density function with altitude is approximated with the α-Chapman model, the effective scale height at the Swarm A altitude is calculated and it is compared with the effective scale height at hmF2. A general conclusion is that the effective scale height in the topside at ~450 km exhibits a diurnal variation with highest values in the early morning and evening sectors, while at hmF2 it gets its maximum values at noon. At night, the effective scale height tends to increase with altitude, however in the daytime, its behavior is more complex. At local scale, evidence for connection between spread F irregularities and high variability in the topside effective scale height is reported. Although the analysis is in progress to include data from the whole Swarm mission, these preliminary results indicate the potential to further exploit Swarm and Digisonde data for effective scale height modeling and for setting up a nowcasting system for the probability of occurrence of ionospheric instabilities in the topside ionosphere based on the bottomside stratification.