LOFAR Lightning Data: Accuracy in Polarization Reconstruction

The polarization of VHF radio signals emitted by lightning can help shed light on the intricate science of lighting propagation, through the direction of the corona VHF emission. However, this lightning radio polarization is not easily measured and, thus, understood. Employing the LOFAR radio telescope, we use a near-field beamforming algorithm (TRI-D) that coherently sums antenna voltages while accounting for the antenna function. This allows us to reconstruct VHF source location and polarization in 3 dimensions. In this work, we evaluate the accuracy of these unparalleled results. Performing a Monte Carlo error analysis, we simulate the antenna voltage signal resulting from a point-like dipole, which is then reconstructed with the imager. The difference between the input and the reconstructed source parameters gives us an approximation of the polarization error bars. We find that the polarization error is at maximum 12 degrees. This value fluctuates with varying source location and angle suspended between the polarization vector and the radial vector. We are testing the polarization reconstruction accuracy for radio point-like sources, background noise, and extended sources. We will present a comprehensive report on these results and their interpretation, our technique, and the imaging algorithm.