The LOw Frequency ARray (LOFAR) radio telescope, a network of stations spread across Europe, is being used to track how disturbances in the ionosphere—the electrically charged layer of the upper atmosphere—bend and disrupt radio waves passing through it. This matters because the ionosphere is constantly shifting, shaped by solar activity and space weather. Irregularities in its plasma density can cause radio signals to flicker or fade, a phenomenon called scintillation. This disrupts GPS navigation, satellite communications, and radar systems that underpin modern infrastructure. Current models struggle to predict these disruptions because they lack detailed, real-time observations of the ionosphere’s fine-scale structure. By exploiting LOFAR’s wide bandwidth and continental baseline, the RISER project will map ionospheric irregularities from tens of metres to hundreds of kilometres across both space and time. Combining LOFAR data with radar, GPS, and ground-based sensors, the research aims to characterise how these irregularities form and move. Success would improve forecasting of space-weather impacts on radio propagation, enabling better mitigation strategies for communications and navigation systems. The project also seeks to correlate these disturbances with solar and geomagnetic activity across a full solar cycle, deepening fundamental understanding of long-term ionospheric variability.
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Radio waves are subject to a variety of propagation effects when traversing through the ionosphere. These effects depend on the radio wave frequency as well as on the ionospheric conditions that determine the spatial distribution of plasma density along a given ray path. Ionospheric propagation effects can be determined at various orders of approximation of the Appleton-Hartree equation for the refractive index. These propagation effects may vary according to the variability of the ionosphere. Irregularities within the ionospheric plasma can disrupt the propagation of trans-ionospheric radio signals, causing scintillation. Within the PhD program, we would aim to leverage LOw Frequency ARray Radar (LOFAR) ability to operating at a wide bandwidth (10 to 240 MHz) and a network of LOFAR stations across Europe to monitor ionospheric induced perturbations on radio waves. LOFAR is capable of producing dynamic spectra that can used to investigate the dynamic ionospheric structure. The current works of LOFAR has already demonstrating its effectiveness in identification of F region and travelling ionospheric disturbances within the lower E region. Furthermore, multi-station imaging has been able to identify sporadic E layers within the ionosphere, mapping its fine-scale morphology and its spatial movement in two dimensions across the LOFAR's continental baseline. Collectively, these results demonstrate LOFAR ability to characterise ionospheric variability from tens of metres to hundreds of kilometres across both space and time. Whereby using LOFAR data, alongside supporting datasets such as incoherent scatter radars, GNSS data, and any suitable ground measurement data such as ionosondes and magnetometers to characterise the formation and the dynamics of ionospheric irregularities. Through combined multi-instrument observations and advanced data analysis techniques, we can investigate how various space weather conditions can affect radio-wave propagation. Further, how such insights can then be used as a tool for forecasting and mitigation strategies for real-life applications. This strand of the research could then explore correlating such identification of ionospheric irregularities with the broader solar and geomagnetic activity, particularly across a full solar cycle, aiming to understand the long-term variability in the ionosphere. This approach will improve our understanding of how fluctuations in space weather drivers can impact the propagation effects of trans-ionospheric radio signals. The RISER (Radio Investigations for Space Environment Research) project will help us understand more of these ionospheric dynamics by using LOFAR spectral imaging of the ionosphere and plasmasphere.
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