Correlated Lightning Electric Field and High-Speed Video Observations of Recoil Leaders Recorded in Rzeszow, Poland

From an electromagnetic compatibility perspective, it is desirable to study all stages of lightning channel development and the corresponding electromagnetic fields. The sequence of lightning electric field signatures of K-changes was recorded by the Lightning Observatory in Rzeszow during the same intracloud (IC) lightning flash and was partially seen by a high-speed video camera. Two of those K-changes corresponding to visible recoil leaders were characterized in detail. Their microsecond scale E-field waveforms revealed an initial burst of submicrosecond impulses followed by a relatively slower and very regular oscillatory-like signature, which is not common for such type of lightning phenomena. The frequency of the oscillations estimated using power spectrum density analysis was about 1.43 MHz for both recoil leaders. A malfunction of the registration system was excluded because other K-changes within this IC lightning flash did not reveal such oscillatory features. Time domain comparison of E-field and high-speed video registrations suggested that discussed E-field signatures of recoil leaders occurred just after their attachment to existing positive leader channels. Such well-pronounced and regular oscillatory-like E-field lightning signatures state a considerable treat to electronics in ground structures and flying objects.