Ionospheric Scintillation observed by LOFAR PL610 station

Due to their low intensity, ionospheric scintillations in the middle latitude region are difficult to observe. However, scintillations intensity increases at lower frequencies. Those below 90 MHz, covered by LOFAR, enable scintillation measurements in mid-latitude region. Long-term observations, with the use of PL610 station, allow the study of weak scintillation climatology, unavailable for measurement led with other methods. The developement of functional tool for the scintillation parameters analysis described in the paper enabled the study of scintillations in the mid-latitude region and future application to the data collected by LOFAR.

LOFAR PL610 station in Borowiec (23E,50N) regularly observes ionospheric scintillation using signals from the 4 strongest radio sources, members of LOFAR A-team: Cas A, Cyg A, Vir A and Tau A. The measurements are taken by LBA antennas at frequencies in the range of 10-90 MHz. Since 2018 we have collected more than 8000 hours of observations. In this work research, we present the results of the automatic s4 calculation system based on our observations. The observations are led in 4-bit mode, for 4 independent sources, with sampling of 10 Hz at 244 subbands. Sources are selected automatically depending on their visibility. Due to the fact that natural radio sources are relatively weak and beamforming is not ideal, the data are noisy. In order to improve the quality of data, the measured amplitudes are filtered and S4 index is computed for each beamlet. All processed data are stored in a database and enable in-depth analysis of scintillation behavior in the mid-latitude region.

We look at the intrinsic features of the observation: dependence on the geometry of the measurement, impact of RFI depending on the strength of the radiosource, the observation frequency then show the dependence of scintillation on the global conditions caused by space weather.