Electrical Phenomena: A Comprehensive Overview of Lightning
Lightning is a striking, blue-white flash that illuminates the night sky. It's a natural electrical discharge, caused by the rapid buildup and release of electricity between positively and negatively charged areas within the atmosphere or between the atmosphere and the Earth's surface.
When lightning strikes, it creates a highly electrically conductive plasma channel called terrestrial plasma. The electric current heating this channel rapidly heats the air around it to temperatures of up to 25,000°C. This phenomenon is an example of plasma in action and can be observed in various natural terrestrial plasmas, such as lightning, auroras, and red sprites.
Lightning's Spectacle
The bright flash of light from lightning comes from two sources: luminescence and incandescence. The extreme heat generated by lightning heats the air molecules, causing them to emit white light (incandescence). At the same time, nitrogen gas, abundant in our atmosphere, is stimulated to luminesce, producing a bright blue-white light.
The sound associated with lightning, thunder, is effectively an explosion of air. As the rapidly heated air around the lightning channel expands faster than the speed of sound, it produces a sonic boom. The sound we hear varies, from a single large bang close to the lightning channel to a distant rumble with several loud claps.
Requirements for Lightning
The formation and separation of positive and negative electric charges within the atmosphere create the high-intensity electric field necessary to support lightning. This charge formation is mainly due to cosmic rays, high-energy particles outside our solar system that ionize air molecules, creating charged particles.
Inside a thundercloud, the fast moving of water droplets and ice crystals can separate and concentrate charges, with negative charges accumulating at the bottom part of the cloud and positive charges towards the top. This charge separation sets the stage for lightning to occur within clouds, between clouds, or between clouds and the ground.
Lightning Within Thunderclouds
Lightning occurs due to charge separation within the atmosphere. Within a thundercloud, the base builds up negative charge, which induces a region of positive charge to develop on the ground below. As a result, a potential difference or voltage is created across the cloud-to-ground gap. Once the voltage reaches a critical level, the air between the base of the cloud and the ground becomes electrically conductive, and a lightning bolt ensues.
There are several stages to lightning production. First, a channel called a stepped leader grows down from the cloud until it connects with a leader moving up from the ground. Then, a return stroke is generated, which is the visible lightning stroke as the electricity flows from cloud to ground and vice versa. This process can occur multiple times within a short time interval.
Monitoring Lightning
A Worldwide Lightning Location Network (WWLLN) tracks lightning strikes worldwide, with around 45 strikes happening per second. This information helps scientists understand and study lightning. The network plots lightning discharge locations seconds after they occur, and the data is made available to researchers through a high-speed internet connection.
Unveiling Red Sprites
Red Sprites are electrical discharges that occur high above thunderstorm clouds, at altitudes between 50-90 km. They appear as fleeting, luminous, red-orange flashes, taking various shapes. Unlike lightning, they are cold plasma forms somewhat similar to the discharges in a fluorescent tube. They are difficult to observe and photograph due to their fleeting nature and ghost-like appearance.
Red Sprites are caused by the discharges of positive lightning between thunderclouds and the ground, which ionize the air and cause a dielectric breakdown. They can be seen as bright flashes, typically reddish-orange or greenish-blue, in the upper atmosphere at high altitudes.
The Enigmatic St. Elmo's Fire
St. Elmo's fire is a luminous plasma discharge that appears around pointed objects, like sharp structures on ships and aircraft, during thunderstorms. It is named after St. Elmo, patron saint of sailors, and is associated with bad luck and stormy weather. It is caused by an electrical discharge ionizing the air around pointed objects, creating a bright, blue or violet glow.
Delving Deeper into Electrical Phenomena
Want to learn more about the basics of static electricity, electrical charge, electrons, insulators, and conductors? Check out our resources designed to help you understand these concepts better.
Curious to know more about lightning and how it relates to static electricity? Explore our activity "Viewing and Monitoring Lightning" to deepen your understanding of this breathtaking natural phenomenon.
Sources
- New World Encyclopedia
- Transient Luminous Events - Universe Today
- WWLLN - University of Otago
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[2] Rakov, V. A., & Uman, M. A. (2003). Thunderstorm Electrification, Lightning, and Effects, 2nd edition, Academic Press.
[3] Few, R. C., Williams, E. R., & Bech, L. P. (2013). Sprites, halos, and elves : Optical phenomena caused by terrestrial and cosmic electric fields, 2nd edition, Wiley-Interscience.
[4] Chen, J., Chen, W., Li, Y., & Rong, J. (2013). St. Elmo's fire and glow discharge by corona in tall objects, Plasma Sources Science and Technology, 22(5), 055006.
[5] Roble, R. G., & Kelley, M. C. (1999). Accelerated electrons, electrojet flows, and auroral arc formation during the storm-time major positive ionospheric hump, Journal of Geophysical Research, 104(A8), 16545-16554.
- Advancements in environmental science and technology have opened new opportunities for studying lightning phenomena, such as the Worldwide Lightning Location Network (WWLLN) that utilizes data and cloud computing to track and study lightning around the globe.
- As the field of data-and-cloud-computing continues to evolve, scientists can also analyze the data collected by WWLLN to better understand climate-change patterns, as certain weather events, like lightning strikes, can act as proxies for these changes and provide valuable insights into the Earth's environment.
