The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. The electric current of the return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning.
Dwyer, Robert Brown, Jennifer Wilson. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud — the greater the accumulated charge, the higher the electrical field.
Cutoff of an extended negative leader from its origin which creates a new bidirectional leader in which the positive end strikes the ground, commonly seen in anvil-crawler spider flashes.
One theory postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown. In positive breakdown, the spark moves downward from a positive to a negative region. This heat causes surrounding air to rapidly expand and vibrate, which creates the pealing thunder we hear a short time after seeing a lightning flash.
About 2, people are killed worldwide by lightning each year. Cloud to ground CG [ edit ] Cloud to ground lightning Cloud-to-ground CG lightning is a lightning discharge between a thundercloud and the ground.
Over the past few decades, researchers have gained a better understanding of how the charges become separated in thunderclouds. These sferics are registered at the 60 WWLLN receiving stations around the world and provide a near real-time information dataset.
Some of the molecules may move quickly enough to break away from the surface of the liquid and carry heat away in the form of a vapor or gas.
Once the voltage reaches a certain strength, the air between the base of the cloud and the ground develops an electrical conductivity.