Fig. 3: Simultaneous space and ground measurements of a superbolt.

(Left) Space and (right) ground simultaneous measurements of a superbolt (1.2 MJ) detected by WWLLN with t = 0 at 2013/01/23-17.43.55.121 UTC. In space, we display the Van Allen Probes (RBSP) burst-mode measurements versus time of a the electric field power spectral density (PSD in V²/m²/Hz) measured by EFW, b the evolution of the squared electric field (intensity) and estimated time at the satellite of all WWLLN-detected lightning strokes in the time window (dashed vertical lines), and c the satellite-detected waveform with the survey acquisition and burst integration windows. (right) On the ground, we display (with same units) the evolution of d the electric field PSD in V²/m²/Hz and of e the squared electric field, f the electrical field waveform and g its zoom. The electric field PSD (a) has a characteristic descending tone shape in space (between t ~ 0.4–0.6 s) but shows a second wave (starting at t ~ 0.6 s) that is the bounce reflection of the primary wave. The sharp rising tone just prior to the descending tone shape (for frequencies within 2 × 10² and 9 × 10³ Hz) is an anti-aliasing filter effect with a fold over of the power above the top frequency that should be disregarded. The estimated median squared electric field (in mV²/m²) (following²²) of all other lightning is reported in b with green circles (#2–#10) and are found to be much lower than the superbolt’s intensity and its estimate (#1 green circle with a red contour) (more detail in Supplementary Table 4). The superbolt frequency decreases below 400 Hz (deep in the whistler-mode hiss wave band) after 2 s (a). See Supplementary Fig. 6 for more detail on space measurements and Supplementary Fig. 7 for more detail on ground-based measurements.