A rare type of lightning has been scratching your head since the late 1970s. “Superbolts” are the most powerful lightning on Earth, with discharges so strong that they cannot be reproduced in the laboratory. The bolts also display geographic and seasonal attributes opposite to those of regular lightning, which adds to their mystery.
“We don’t yet understand how superbolts can be so powerful,” said Jean-François Ripoll, senior scientist at the Atomic Energy Commission (CEA) near Paris, France. And unlike traditional lightning, which occurs more often in summer and over land, super lightning occurs more often in winter and over water. “We don’t know why,” he said.
Amidst the many unknowns, scientists are using satellites to define the unusual attributes of superbolts. A 2020 study of optical satellite data showed that some of the brightest lightning – up to 1,000 times brighter than normal lightning – are indeed a physically unique type of lightning, and not due to an error in the interpretation of the measurement.
In a 2021 study, Ripoll and his colleagues confirmed the extreme power of superbolts by measuring their electromagnetic waves. This electromagnetic phenomenon, they discovered, is not limited to the Earth’s atmosphere; it extends into space.
Lightning is a natural source of electromagnetic energy that extends to the very low frequency (VLF) range. Scientists have shown that the VLF waves transmitted into space by superbolts are much more powerful than those transmitted by typical lightning. “Electromagnetic waves like these are rare because of lightning signals in space,” Ripoll said. “We doubted that power until we could pair it with a superbolt.”
To make the connection, the researchers worked to match the spatial detections of superbolts with multiple detections on the ground. The map at the top of this page shows detections of superbolts (energies greater than 1 megajoule) between 2012 and 2018. The blue dots are ground detections, from the World-Wide Lightning Location Network (a network of stations among more than 50 universities and institutions headed by Robert Holzworth at the University of Washington), the ECLAIR measurement campaign conducted from CEA ground stations, and Metéorage ground stations. The purple dots are where the spatial detections from NASA’s Van Allen probes overlap with the detections on the ground.
In this dataset, two superbolts had enough overlapping soil and space data for a detailed study. One of them, noted by the big pink dot on the map, is shown on the spectrogram above. This graph shows the electrical component of the electromagnetic signal of the superbolt detected from space.
Note that the signal from the first two comma-shaped detections (red) is much stronger than the subsequent signals. These two powerful waves are associated with the super lightning, followed by less powerful waves associated with many typical lightning strikes.
“Some of these super lightning bolts can have up to 1,000 times more energy than typical lightning,” Ripoll said. Such bolts are capable of producing more damage than typical lightning if they were to strike the right spot on Earth.
In space, however, electromagnetic waves have a potentially useful application in that they can deflect so-called “killer electrons” trapped in near-Earth space where they can damage the electronics of satellites by. orbit. “Potentially, this electromagnetic power can shield our assets from these electrons,” Ripoll said. “We study waves, electrons and wave-particle interactions for this reason. We are happy to know that these waves are real and based on physics. “
Images from NASA’s Earth Observatory by Joshua Stevens, using data courtesy of Ripoll, J.-F., et al. (2021). Kathryn Hansen story.