How Accurately Does LOFAR Reconstruct Lightning? Point and Extended Source Analysis

The polarization of VHF radio emissions from lightning offers valuable insight into the complex physics of lightning propagation by revealing the orientation of streamer-driven VHF radiation. Measuring and interpreting this polarization, however, remains challenging. In this work, we use the LOFAR radio telescope in combination with the latest near-field beamforming technique (A-TRID) that coherently combines antenna voltages while incorporating the full antenna response. This approach enables three-dimensional reconstruction of both the location and polarization of VHF lightning sources. In this presentation, we assess the accuracy of these results by means of a Monte Carlo error analysis. We simulate antenna voltage signals produced by a point-like dipole and an extended source, a cluster of indentical dipole emitters. Subsequently, we reconstruct them using the imaging algorithm. By comparing the reconstructed source parameters with the known inputs, we obtain an estimate of the location and polarization uncertainties. For point sources, we observe a sub-meter reconstruction accuracy in three-dimensional location; and an average one-degree reconstruction accuracy in three-dimensional polarization. These values vary with the source location and with the angle between the polarization vector and the radial vector. For extended sources, we see the reconstructed location (the source size) is smaller than the input; by up to a factor of two. The polarization reconstruction accuracy is different along the two axes; a sub-degree reconstruction accuracy along the azimuthal direction and an average 7.5-degree reconstruction accuracy along the zenithal direction. This report offers a comprehensive evaluation of the results, alongside a breakdown of our technical approach and algorithmic framework.