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Description
LOw-Frequency ARray (LOFAR) consists of a European array of 52 radio telescopes designed for use, either collectively as an international interferometer or independently as separate stations. There are three LOFAR stations, localised in Poland, one of which is under the ownership of the Space Research Centre of the Polish Academy of Sciences. Positioned in Borówiec, Poland, the PL610 LOFAR station operates at the frequency range of 10 - 240 MHz, enabling the observations of astronomical sources at the lowest frequencies available on Earth.
Due to its design and operating frequencies, the LOFAR radio telescope is not limited to radio-astronomical observations. In that context, the Space Research Centre of the Polish Academy of Sciences utilises the station to monitor the ionosphere and observe the effects of space weather.
The previous studies confirmed the feasibility of measuring ionospheric gradients using a single LOFAR station by observing the changes in radio source position.
In our work, we show that the ionosphere significantly impacts the radio source position that is directly connected to the horizontal ionisation gradient.
To investigate this gradient, we measured the positions of the strongest astronomical radio sources – called the A-Team (CasA, CygA, TauA, and VirA) – observed in the LOFAR frequency range (10 – 90 MHz). Due to its high time resolution (1 s), the method allows the observation of small-scale structures, which can be related to ionospheric scintillation. Moreover, it enables the observation of medium-scale structures moving over the LOFAR station.
In the following work, we present selected cases of observed structures recorded moving over the station during the observations.
