The 3D Polarization of Recoil Leaders

We have recently developed a new 3D beamforming algorithm, using data from the LOw Frequency ARray (LOFAR) radio telescope (in the 30-80 MHz band), that is capable of resolving even the most complex lightning phenomena with meter and nanosecond scale accuracy. Because it operates in full 3D, this algorithm inherently extracts and accounts for the 3D polarization of the VHF sources. Here we demonstrate the full power of this technique by extracting the full 3D polarization of multiple sections of recoil leaders. We confirm previous work that showed that recoil leaders have significant polarization perpendicular to the lightning channel, likely due to charge flow between the lightning channel core and corona sheath. However, we also show that recoil leaders can also have significant polarization parallel to the channel as well. In addition, we show that the ratio of parallel-to-perpendicular polarization is strongly correlated with faster and more intensely emitting recoil leaders. We will argue that this could be due to faster recoils causing the electric field parallel to the channel to change more rapidly, and if the electric field changes rapidly enough than the recoil leader can create streamers parallel to the lightning channel which are much more strongly emitting than streamers perpendicular to the lightning channel.