A Strong Pulsing Nature of Negative Intracloud Dart Leaders Accompanied by Regular Trains of Microsecond-Scale Pulses

We report the first observations of negative intracloud (IC) dart-stepped leaders accompanied by regular trains of microsecond-scale pulses, simultaneously detected by shielded broadband magnetic loop antennas and the radio telescope Low Frequency Array (LOFAR). Four investigated pulse trains occurred during complicated IC flashes on 18 June 2021, when heavy thunderstorms hit the Netherlands. The pulses within the trains are unipolar, a few microseconds wide, and with an average inter-pulse interval of 5–7 μs. The broadband pulses perfectly match energetic, regularly distributed, and relatively isolated bursts of very high frequency sources localized by LOFAR. All trains were generated by negative dart-stepped leaders propagating at a lower speed than usual dart leaders. They followed channels of previous leaders occurring within the same flash several tens of milliseconds before the reported observations. The physical mechanism remains unclear as to why we observe dart-stepped leaders, which show mostly regular stepping, emitting energetic microsecond-scale pulses.</p

Interferometric imaging of intensely radiating negative leaders

The common phenomenon of lightning still harbors many secrets and only recently a new propagation mode was observed for negative leaders. While propagating in this `Intensely Radiating Negative Leader\u27 (IRNL) mode a negative leader emits 100 times more very-high frequency (VHF) and broadband radiation than a more normal negative leader. We have reported that this mode occurs soon after initiation of all lightning flashes we have mapped as well as sometimes long thereafter. Because of the profuse emission of VHF the leader structure is very difficult to image. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily built for radio-astronomy observations. For this reason, as part of the present work, we have refined our time resolved interferometric 3-Dimensional (TRI-D) imaging to take into account the antenna function. The images from the TRI-D imager show that during an IRNL there is an ionization front with a diameter in excess of 500~m where strong corona bursts occur. This is very different from what is seen for a normal negative leader where the corona bursts happen at the tip, an area of typically 10~m in diameter. The observed massive ionization wave supports the idea that this mode is indicative of a dense charge pocket

Interferometric imaging of intensely radiating negative leaders

The common phenomenon of lightning still harbors many secrets and only recently a new propagation mode was observed for negative leaders. While propagating in this "intensely radiating negative leader"(IRNL) mode a negative leader emits 100 times more very-high frequency (VHF) and broadband radiation than a more normal negative leader. We have reported that this mode occurs soon after initiation of all lightning flashes we have mapped as well as sometimes long thereafter. Because of the profuse emission of VHF the leader structure is very difficult to image. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily built for radio-astronomy observations. For this reason, as part of the present work, we have refined our time resolved interferometric 3-dimensional (TRI-D) imaging to take into account the antenna function. The images from the TRI-D imager show that during an IRNL there is an ionization front with a diameter in excess of 500 m where strong corona bursts occur. This is very different from what is seen for a normal negative leader where the corona bursts happen at the tip, an area of typically 10 m in diameter. The observed massive ionization wave supports the idea that this mode is indicative of a dense charge pocket

The Initial Stage of Cloud Lightning Imaged in High Resolution

With LOFAR we have been able to image the development of lightning flashes with meter-scale accuracy and unprecedented detail. We discuss the primary steps behind our most recent lightning mapping method. To demonstrate the capabilities of our technique we show and interpret images of the first few milliseconds of two intra-cloud flashes. In all our flashes the negative leaders propagate in the charge layer below the main negative charge. Among several interesting features we show that in about 2~ms after initiation the Primary Initial Leader triggers the formation of a multitude (more than ten) negative leaders in a rather confined area of the atmosphere. From these only one or two continue to propagate after about 30~ms to extend over kilometers horizontally while another may propagate back to the initiation point. We also show that normal negative leaders can transition into an initial-leader like state, potentially in the presence of strong electric fields. In addition, we show some initial breakdown pulses that occurred during the primary initial leader, and even during two "secondary" initial leaders that developed out of stepped leaders.Comment: Submitted to Journal of geophysics research: Atmosphere

A distinct negative leader propagation mode

The common phenomenon of lightning still harbors many secrets such as what are the conditions for lightning initiation and what is driving the discharge to propagate over several tens of kilometers through the atmosphere forming conducting ionized channels called leaders. Since lightning is an electric discharge phenomenon, there are positively and negatively charged leaders. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily build for radio-astronomy observations. It is observed that a negative leader rather suddenly changes, for a few milliseconds, into a mode where it radiates 100 times more VHF power than typical negative leaders after which it spawns a large number of more typical negative leaders. This mode occurs during the initial stage, soon after initiation, of all lightning flashes we have mapped (about 25). For some flashes this mode occurs also well after initiation and we show one case where it is triggered twice, some 100 ms apart. We postulate that this is indicative of a small (order of 5 km2) high charge pocket. Lightning thus appears to be initiated exclusively in the vicinity of such a small but dense charge pocket

Erratum: The solar orbiter radio and plasma waves (RPW) instrument (Astronomy and Astrophysics (2020) 642 (A12) DOI: 10.1051/0004-6361/201936214)

The erratum concerns Fig. 9 entitled "Antenna radio-electrical properties" for which some of the parameters are not correct. The new figure with new parameters is provided in Fig. 1 of this corrigendum. Fig. 1. Corrected Antenna radio-electrical properties. (Figure Presented)

Plotting codes for figure 3 in &quot;Lightning at Jupiter pulsates with a similar rhythm as in-cloud lightning at Earth&quot;

The file &quot;Figure_3_code_pol.pro&quot; is a source code written in the IDL programming tool for plotting all panels in Figure 3 in the manuscript &quot;Lightning at Jupiter pulsates with a similar rhythm as in-cloud lightning at Earth&quot; using the data provided as a supporting Excel file to the paper

Magnetic loop antennas data for the manuscript &quot;A strong pulsing nature of negative intracloud dart leaders accompanied by regular trains of microsecond-scale pulses &quot;

Data used in the analysis of sequences of magnetic field microsecond scale pulses occurring during the development of extensive intracloud flashes. The antennas measure the time derivative of the magnetic field fluctuations. Measurements conducted by the Antenna 2 are used to analyze event C1. Measurements conducted by the Antenna 1 are used to analyze events C5, C9-1 and C9-2