1,2,1,2,1,2,1,2,5- 1Netherlands Institute for Radio Astronomy (ASTRON), Dwingeloo, Netherlands
- 2Kapteyn Astronomical Institute, University of Groningen, Groningen, Netherlands
- 3State Key Laboratory of Severe Weather Meteorological Science and Technology & CMA Key Laboratory of Lightning, Chinese Academy of Meteorological Sciences, Beijing, China
- 4Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA
- 5Department of Physics & Astronomy and Space Science Center (EOS), University of New Hampshire, Durham, NH, USA
In this work, we use lightning observations obtained by the LOFAR radio telescope to investigate the propagation dynamics of High Altitude Negative Leaders (HANLs), which have altitudes above 7 km. Operating in the very high frequency (VHF) range, LOFAR can probe lightning processes
occurring deep within the cloud at high altitudes with sub-meter precision and 100 ns integration times [2].
HANLs exhibit step lengths exceeding 100 m, an order of magnitude larger than those of negative leaders observed at lower altitudes [1]. The plasma processes underlying these HANL steps remain unknown, and it is unclear whether HANLs propagate through the same mechanism as lower altitude negative leaders. To study these structures with enhanced precision and sensitivity, we apply ATRI-D, a near-field interferometric beamforming algorithm, to LOFAR data.
Our observations reveal that the dynamics of HANL steps is increasingly complex at smaller scales. At large scales (kilometers and tens of milliseconds), HANL propagation appears as a sequence of discrete corona flashes. In contrast, on smaller scales (tens of meters and milliseconds), these “corona flashes” resolve into several branched networks of filaments that initiate at different times and locations. In addition, we find that each branched network begins with an intense VHF pulse occurring within 10 m of a previously formed filament. We will discuss some of the potential physics implications of these results.
[1] O. Scholten et al.; Distinguishing features of high altitude negative leaders as observed with LOFAR. Atmospheric Research, 260:105688, October 2021. ISSN 0169-8095. doi: 10.1016/j.atmosres.2021.105688.
[2] O. Scholten, M. Lourens et al.; Measuring location and properties of very high frequency sources emitted from an aircraft flying through high clouds. Nature Communications, 16(1), November 2025. ISSN 2041-1723. doi: 10.1038/s41467-025-65667-2.
How to cite: Lourens, M., Hare, B., Scholten, O., Sterpka, C., Turekova, P., Wu, B., Cummer, S., Dwyer, J., and Liu, N.: Fine-Scale Structure of High-Altitude Negative Leader Steps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11132, https://doi.org/10.5194/egusphere-egu26-11132, 2026.
