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We present broadband ionospheric scintillation observations of highly definedsymmetric quasi-periodic oscillations (QPO: Maruyama 1991) caused by plasmastructures in the midlatitude ionosphere using the LOw Frequency ARray (LOFAR:van Haarlem et al., 2013). Two case studies are shown, one from 15th December2016, and one from 30th January 2018, in which well-defined main signal fadesand secondary diffraction fringing are observed. In particular, the broadbandobserving capabilities of LOFAR permit us to see considerable frequencydependent behaviour in the QPOs which, to our knowledge, is a new result. Weextract some of the clearest examples of scintillation arcs reported in anionospheric context, from delay-Doppler spectral analysis of these two events.These arcs permit the extraction of propagation velocities for the plasmastructures causing the QPOs ranging from 50 - 200 ms$^{-1}$, depending on theassumed altitude. The spacing between the individual plasma structures rangesbetween 5 - 20 km. The periodicities of the main signal fades in each eventand, in the case of the 2018 data, co-temporal ionosonde data, suggest thepropagation of the plasma structures causing the QPOs is in the E-region. Eachof the two events is accurately reproduced using a Gaussian perturbation phasescreen model. Individual signal fades and enhancements were modelled usingsmall variations in total electron content (TEC) amplitudes of order 1 mTECu,demonstrating the sensitivity of LOFAR to very small fluctuations inionospheric plasma density. To our knowledge these results are among the mostdetailed observations and modelling of QPOs in the literature.

Observations of high definition symmetric quasi-periodic oscillations in the mid-latitude ionosphere with LOFAR