What is Lightning?
Lightning is an enormous electrostatic discharge between the cloud and the ground, other clouds, or within a cloud. It is a gigantic electrical spark that results from billions of volts of natural static electricity. This is actually the same kind of electricity that can shock you when you touch a doorknob! Lightning is usually associated with thunderstorms and rain. Scientists still do not understand 100% how lightning works or how it interacts with the upper atmosphere or the earth’s electromagnetic field. Scientists know and understand the cloud conditions needed to produce lightning, however, the time and location of upcoming lightning strikes cannot be predicted.
Lightning is an essential part of the life cycle. The body contains molecules known as proteins, which are composed of nitrogen. All of life depends on nitrogen to survive. While our atmosphere is significantly made up of nitrogen, we do not receive nitrogen from the air that we breathe.
What Causes Lightning?
There is still some debate on exactly how lightning forms, however, scientists do know what conditions are needed to produce lightning. Generally lightning begins with the water cycle. Moisture accumulates in the atmosphere causing clouds to form; these clouds essentially contain millions of water droplets and ice crystals suspended in the air. As evaporation and condensation continues with the water cycle, these beads collide with other moisture and ice in the air. During these collisions electrons are knocked off of the rising moisture, thus creating a charge separation.
Ice is often central to the development of lightning. As stated earlier, with the rising and sinking within a storm there are various collisions among particles. Positively charged ice crystals generally move to the top, while negatively charged ice particles drop to the middle and lower parts of the storm. Here massive charge variations (electrical differences) develop.
The “Charge Reversal Concept” states that falling graupel (small ice pellets) become negatively charged while small supercooled cloud droplets that strike then bounce off the graupel become positively charged. Cloud temperature can affect the “charge sign” of the graupel. If the temperature is below -10C then the graupel takes a negative charge and the supercooled cloud droplets take a positive charge. The supercooled cloud droplets rise on updrafts to the top of the storm while the graupel pellets fall and melt in the lower regions of the storm.
Overall, lightning occurs when there is charge separation in a cloud. As a thunderstorm grows, electrical charges build up within the cloud, causing charge of the opposite potential to gather at the ground below. The attraction between positive and negative charges can grow strong enough to overcome the air’s resistance to electrical flow. The cloud begins sending down charges called stepped leaders in the atmosphere. Racing toward each other, they connect and complete the electrical circuit. Charge from the ground then surges upward at nearly one-third the speed of light and we see a bright flash of lightning.