Optical and radio characterization of continuing current lightning with ASIM, GLM and ELF sensors

Lightning with continuing current is a special type of cloud-to-ground flash that can damage electrical systems and cause forest fires, with implications to air quality. Therefore, their precise characterization and early detection are crucial. Here we use a combination of space-based (Atmosphere-Space Interaction Monitor and Geostationary Lightning Mapper) and ground-based (Earth Networks Total Lightning Network and Extreme Low Frequency magnetic field antenna) instruments to systematically identify continuing current lightning between June 1, 2018 and December 31, 2021 in the Contiguous United States. Matched flashes are analyzed using two approaches. In the first, we classify the flashes according to the approximate models of Fairman and Bitzer (2022) as either having continuing current or not. In the second approach, we classify cloud-to-ground flashes reported by the Earth Networks Total Lightning Network using Δ B , a sensitive magnitude derived from Extreme Low Frequency magnetic signals. Δ B quantifies the difference in the average magnetic field signal during the 20 ms before and after the return stroke. A threshold of 0.15 pT was established based on simultaneous observations of a continuing current flash on April 22, 2017, recorded by an Extreme Low Frequency magnetic antenna in Cabo Verde and the Huntsville, Alabama Marx Meter Array. Significant differences were observed in the dual-wavelength (337.0 nm and 777.4 nm) light curves recorded by the Atmosphere–Space Interaction Monitor for flashes with and without continuing current, suggesting its potential for identifying this type of lightning based on spectral emission. • The combined ELF and dual-wavelength optical recordings of continuing current (CC) lightning show distinct features. • The blue (337.0 nm) to red (777.4 nm) ratio of CC lightning is larger than the one of lightning without CC. • A higher blue to red ratio in CC lightning than in no-CC lightning suggests dominant streamer activity associated to in-cloud leaders as seen from space.