Observations of the interstellar scattering of pulsars with the POLFAR stations

One of the most important effects occurring during the propagation of the pulsar-emitted radio waves through the interstellar medium (ISM) is the temporal pulse broadening caused by the scattering of the signal. Our latest studies of this phenomenon, which were performed for the largest sample of pulsars used for this purpose, have shown that the amount of the observed scattering strongly depends on the observing frequency. However, the slope of the dependence is different from the theoretical predictions based on simple scattering models of the turbulent ISM. Low frequency observations are crucial for the study of the scattering phenomenon, since it is at frequencies below a few hundred megahertz where the effects of scattering are the strongest. Currently for pulsar observations we are using all three POLFAR (POlish Low Frequency ARray) stations, which are a part of the International Low Frequency Array (ILT) telescope. The wide bandwidth of the telescope's receivers allows us to study the frequency evolution of interstellar scattering with a single observation. We will present the first results of this project.