Particles power the lightning
After discovering that the voltage of thunderclouds is too low to cause lightning, scientists believe high-energy protons from space are involved in stripping electrons from molecules to trigger the strikes.
Protons rip electrons loose
High-energy protons in cosmic radiation constantly strike Earth’s upper atmosphere, where they rip electrons loose from oxygen and nitrogen molecules, sending showers of electrons down though the atmosphere.
Chain reaction gets out of hand
The shower of electrons strikes a thundercloud, ripping still more electrons loose from air molecules in an outof-control chain reaction. The negatively-charged electrons finally collect in a small area at the bottom of the thundercloud.
Lightning channel spreads in bursts
On the cloud’s lower side, a lightning channel forms in which electrons travel in bursts of 50-100 metres down towards the positively-charged surface of Earth. Before each jerk, the electrons unite at the tip of the lightning channel in 50-microsecond pauses.
Positive electricity travels upwards
The lightning channel branches down from the cloud, and when its longest branch approaches Earth’s surface, positively-charged energy travels upwards towards the lightning channel. The positive path typically originates from high points such as hills and trees.
Lightning strikes
The encounter between the negative lightning channel from the cloud and the positive lightning channel from Earth neutralises the voltage difference. The energy is discharged in a lightning strike that lasts a quarter of a second, triggering 3-4 lightning bolts at intervals of around 0.04 second.