Observing plasma structures at multiple scale sizes in the high-latitude ionosphere with a suite of ground-based instrumentation.

The terrestrial ionosphere is a highly variable medium that affects the propagation of radio waves. Within the ionosphere, large-scale structures, such as polar cap patches, auroral forms, blobs, and polar holes, have been observed. Small-scale irregularities associated with these large-scale structures result from instability processes which can lead to scintillation of trans-ionospheric radio signals, such as those used for Global Navigation Satellite Systems (GNSS). To investigate plasma irregularities and scintillation in the high-latitude ionosphere, the Scales of Ionospheric Plasma Structuring (SIPS) experiment was conducted using a suite of ground-based instrumentation between the 3^rd and 15^th of January 2024.

The aim of the SIPS experiment was to observe the high-latitude ionosphere across several scale sizes, and this required a variety of ground-based instruments, in conjunction with the Swarm satellites. The European Incoherent SCATter (EISCAT) radars were used to measure the plasma parameters, such as density, giving indication to the presence of large-scale plasma structures that were several hundreds of km in size. Medium-scale plasma irregularities, with scale sizes of several km, were inferred from the ground by the LOw Frequency ARray (LOFAR) and the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA). Smaller-scale irregularities less than 500m in scale size were inferred from the scintillation data from ground-based GNSS receivers giving an indication to the scintillation effects. To assist in the interpretation of the results, the Swarm Ionospheric Scintillation (SWIS) methodology was also used, which utilises data from the Swarm satellites to give a spectrum of irregularities to scale sizes down to 500m (Spogli et al., 2022). Using this array of observations, the relationship between irregularities of varying scale sizes could be explored, along with the formation and generation of small-scale irregularities due to instability mechanisms and the subsequent scintillation effects which can occur.

The combination of both ground-based and space-based instruments in this experiment, observing and modelling the ionospheric plasma, gives unprecedented coverage of varying scale sizes which is not possible with individual instrumentation alone. 72 hours of EISCAT observation time was awarded for this experiment which was carried out over 5 nights in January 2024 between 18:00 and 23:59 UT. These experiments yielded a wealth of new results, the most significant of which will be discussed in this presentation.

Spogli, L., Iman, R., Alfonsi, L., Cesaroni, C., Jin, Y., Clausen, L., Wood, A., & Miloch, W. J. (2022). Feasibility of a Swarm Ionospheric Scintillation (SWIS) proxy for L-band scintillation. AGU Fall Meeting 2022.