X-rays and lightning: scientists unlock the secret of positive upward lightning strikes

For the first time, a team from the Ecole Polytechnique Fédérale de Lausanne has measured the X-rays emitted when positive upward lightning strikes. This type of lightning, which rises from the ground towards the clouds, is very rare and dangerous. Lʹexperiment was made possible by state-of-the-art equipment, including high-speed cameras and X-ray detectors.