Prague, April 14, 2026
Illustration of a thunderstorm. Source: istock.com, credit: User9637786_380
Scientists from the Institute of Atmospheric Physics of the Czech Academy of Sciences have published the first detailed study on narrow bipolar events detected over the European continent in the journal Journal of Geophysical Research: Atmospheres. These extremely fast and intense intra-cloud discharges were previously the domain of research in America and Asia; in this regard, European storms represented a major unknown for science.
Narrow bipolar events (NBEs) called also Compact Intracloud Discharges (CIDs) are a specific type of discharge in thunderclouds (with lengths of less than 2 km) that last only a few tens of microseconds. Although spatially small, they represent the strongest natural sources of radio frequency radiation in the high-frequency (HF) and very-high-frequency (VHF) bands. “They radiate approximately ten times more strongly than common cloud-to-ground lightning discharges,” says the lead author of the study, Ivana Kolmašová from the Institute of Atmospheric Physics of the Czech Academy of Sciences.
The scientific team under her leadership analyzed data from 2022 recorded using SLAVIA broadband magnetic sensors at two stations in South-Eastern France (in Provence and on Corsica). In total, the scientists captured and examined thirty-five positive discharges with an average peak current of 43 kA. “The research confirmed that narrower and sharper magnetic field pulses tend to be associated with higher peak currents. Approximately every fourth studied discharge occurred in isolation, without initiating a subsequent common lightning flash. Furthermore, most of these events occurred at the edges of convective cores, near the coldest thundercloud regions with temperatures below
−50 °C,” explained Ivana Kolmašová.
Why were these rare events in thunderclouds previously overlooked in Europe? The study by Czech scientists provides an answer to this as well. Extreme storm conditions requiring development of the overshooting tops of the thounderclouds above the troposphere are less frequent in the temperate latitudes of Europe than in tropical regions, the authors explain.
The confirmation of the occurrence of narrow bipolar events in Europe and the analysis of their meteorological context allow scientists to better understand the internal charge structure of thunderclouds. Data from the French lightning detection network METEORAGE and satellite imagery showed that these discharges originate in regions with ice crystals that are carried away from the active convective centers of the storm. This research thus contributes to a better understanding of the mechanisms leading to the initiation of lightning.
Link to the publication:
- Kolmašová, I., et al. (2026). Properties of positive narrow bipolar events observed in South-Eastern France. Journal of Geophysical Research: Atmospheres. [DOI: 10.1029/2025JD045415]