Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends—called positive and negative leaders1. Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30–300-megahertz frequency band2,3,4,5,6,7,8 that can be remotely sensed and imaged with high spatial and temporal resolution9,10,11. Positive leaders propagate more continuously and thus emit very little high-frequency radiation12. Radio emission from positive leaders has nevertheless been mapped13,14,15, and exhibits a pattern that is different from that of negative leaders11,12,13,16,17. Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders9,12,16,18,19,20, which may lead to current pulses that both reconnect positive leaders to negative leaders11,16,17,20,21,22 and cause multiple cloud-to-ground lightning events1. The disconnection process is thought to be due to negative differential resistance18, but this does not explain why the disconnections form primarily on positive leaders22, or why the current in cloud-to-ground lightning never goes to zero23. Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures—which we call ‘needles’—that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
To obtain the data, readers should submit a support request to the radio observatory via the ASTRON website (http://www.astron.nl). The 2016 flash was from project LC6_003, observation L526419, time stamp D20160712T173455.100Z. The 2017 flash was from LC8 commissioning data, observation L612746, time stamp D20170929T202255.000Z.
The data was processed with software archived at https://github.com/Bhare8972/LOFAR-LIM, version 2018.11.8.
Dwyer, J. R. & Uman, M. A. The physics of lightning. Phys. Rep. 534, 147–241 (2014).
Chen, M. et al. Spatial and temporal properties of optical radiation produced by stepped leaders. J. Geophys. Res. D 104, 27573–27584 (1999).
Hill, J. D., Uman, M. A. & Jordan, D. M. High-speed video observations of a lightning stepped leader. J. Geophys. Res. D 116, D16117 (2011).
Edens, H. E., Eack, K. B., Rison, W. & Hunyady, S. J. Photographic observations of streamers and steps in a cloud-to-air negative leader. Geophys. Res. Lett. 41, 1336–1342 (2014).
Biagi, C. J., Uman, M. A., Hill, J. D. & Jordan, D. M. Negative leader step mechanisms observed in altitude triggered lightning. J. Geophys. Res. D 119, 8160–8168 (2014).
Lyu, F., Cummer, S. A., Lu, G., Zhou, X. & Weinert, J. Imaging lightning intracloud initial stepped leaders by low-frequency interferometric lightning mapping array. Geophys. Res. Lett. 43, 5516–5523 (2016).
Qi, Q. et al. High-speed video observations of the fine structure of a natural negative stepped leader at close distance. Atmos. Res. 178–179, 260–267 (2016).
Jiang, R. et al. Channel branching and zigzagging in negative cloud-to-ground lightning. Sci. Rep. 7, 3457 (2017).
Rison, W., Thomas, R. J., Krehbiel, P. R., Hamlin, T. & Harlin, J. A GPS-based three-dimensional lightning mapping system: initial observations in central New Mexico. Geophys. Res. Lett. 26, 3573–3576 (1999).
Thomas, R. J. et al. Accuracy of the lightning mapping array. J. Geophys. Res. D Atmospheres 109, D14207 (2004).
Stock, M. G. et al. Continuous broadband digital interferometry of lightning using a generalized cross-correlation algorithm. J. Geophys. Res. D 119, 3134–3165 (2014).
Shao, X. M. & Krehbiel, P. R. The spatial and temporal development of intracloud lightning. J. Geophys. Res. D 101, 26641–26668 (1996).
Shao, X. M., Rhodes, C. T. & Holden, D. N. RF radiation observations of positive cloud-to-ground flashes. J. Geophys. Res. D 104, 9601–9608 (1999).
Yoshida, S. et al. Three-dimensional imaging of upward positive leaders in triggered lightning using VHF broadband digital interferometers. Geophys. Res. Lett. 37, L05805 (2010).
Dong, W., Liu, X., Yu, Y. & Zhang, Y. Broadband interferometer observations of a triggered lightning. Chin. Sci. Bull. 46, 1561–1565 (2001).
Shao, X. M., Krehbiel, P. R., Thomas, R. J. & Rison, W. Radio interferometric observations of cloud-to-ground lightning phenomena in florida. J. Geophys. Res. D 100, 2749–2783 (1995).
Edens, H. E. et al. VHF lightning mapping observations of a triggered lightning flash. Geophys. Res. Lett. 39, L19807 (2012).
Heckman, S. Why Does a Lightning Flash Have Multiple Strokes? PhD thesis, Massachusetts Institute of Technology. https://dspace.mit.edu/handle/1721.1/17300 (1992).
Akita, M. et al. What occurs in K process of cloud flashes? J. Geophys. Res. D 115, D07106 (2010).
Mazur, V. The physical concept of recoil leader formation. J. Electrost. 82, 79–87 (2016).
Mazur, V. Triggered lightning strikes to aircraft and natural intracloud discharges. J. Geophys. Res. D 94, 3311–3325 (1989).
Mazur, V. Physical processes during development of lightning flashes. C. R. Phys. 3, 1393–1409 (2002).
Ngin, T. et al. Does the lightning current go to zero between ground strokes? Is there a current “cutoff”? Geophys. Res. Lett. 41, 3266–3273 (2014).
Norden, M. & Bregman, D. J. in 9th International Symposium on Electromagnetic Compatibility Joint with the 20th International Wroclaw Symposium on Electromagnetic Compatibility (EMC EUROPE 2010) 569–575, http://www.astron.nl/sites/astron.nl/files/cms/PDF/EMC%20Lightning%20Final%20ACC.pdf (2010).
van Haarlem, M. P. et al. LOFAR: The LOw-Frequency ARray. Astron. Astrophys. 556, A2 (2013).
Behnke, S. A., Thomas, R. J., Edens, H. E., Krehbiel, P. R. & Rison, W. The 2010 eruption of Eyjafjallajökull: lightning and plume charge structure. J. Geophys. Res. D 119, 833–859 (2014).
Becerra, M. & Cooray, V. A self-consistent upward leader propagation model. J. Phys. D 39, 3708–3715 (2006).
Wang, Z. et al. High-speed video observation of stepwise propagation of a natural upward positive leader. J. Geophys. Res. D 121, 14,307–14,315 (2016).
Malan, D. J. & Schonland, B. F. J. The electrical processes in the intervals between the strokes of a lightning discharge. Proc. R. Soc. Lond. A 206, 145–163 (1951).
Cooray, V. & Arevalo, L. Modeling the stepping process of negative lightning stepped leaders. Atmosphere 8, 245 (2017).
The LOFAR cosmic ray key science project acknowledges funding from an Advanced Grant of the European Research Council (FP/2007–2013)/ERC Grant Agreement number 227610. The project has also received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 640130). We furthermore acknowledge financial support from FOM (FOM-project 12PR304). A.N. is supported by the DFG (research fellowship NE 2031/2-1). T.W. is supported by the DFG (research fellowship NE WI 4946/1-1). This paper is based (in part) on data obtained with the International LOFAR Telescope (ILT) under project code LC6_003. LOFAR25 is the Low Frequency Array designed and constructed by ASTRON. It has observing, data processing and data storage facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d’Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland.
Nature thanks E. Williams and the other anonymous reviewer(s) for their contribution to the peer review of this work.
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
This is a single document that includes significant additional information on our work. Including: description of our imaging technique, additional information about the 2016 and 2017 lightning flashes, additional needles that were imaged in the 2016 and 2017 flashes, additional hypothesis, discussions on the potential for optical observations of needles, and a simple location error analysis.
A 3D animation of the 2017 flash.
A close-up animation of a negative leader in the 2017 flash.
A close-up animation of a segment of positive leader, with needle N4 shown in red.
About this article
Journal of Geophysical Research: Atmospheres (2019)
Chemie in unserer Zeit (2019)
Physik in unserer Zeit (2019)