A leaf lightning can actually cause an electric shock
What are the different types of lightning?
Although we consider lightning to be more like lightning bolting from the sky to the earth, lightning can hit the ground or strike clouds or the air. According to the US National Severe Storm Laboratory, there are five to ten times as many lightning strikes in clouds as there are cloud-to-ground strikes. Here's a look at the different types of lightning strikes that can occur during a thunderstorm.
Lightning from cloud to ground
As the negative charge grows in the base of a thunderstorm, the positive charge accumulates in the surface of the earth and shadows the storm wherever it goes. This is responsible for almost all cloud to ground lightning strikes (see picture above). In a bolt of lightning from cloud to ground, a tiered leader lurches down from the negative cloud base, intercepted on his way by an ionized column of air known as a "positive streamer" that hits them from the positively charged ground. When the two connect, a violent electrical current rushes between the cloud and the ground, forming lightning. Sometimes multiple positive streamers compete for the same tiered leader.
Almost any grounded object or organism under a thunderstorm can attract a tiered leader, but lightning is lazy. The closer the better. Trees, tall buildings, towers, and antennas are preferred targets and, contrary to popular wisdom, lightning can strike twice.
Intracloud and cloud-to-cloud lightning
About three-quarters of all lightning bolts on earth never leave the cloud in which they formed and are content to find another region of oppositely charged particles in the storm. These strikes are known as "intracloud lightning", but sometimes also called "leaf lightning" when we see them illuminate a glowing leaf on the cloud surface. "Spider Lightning" (see photo below) occurs when branching bolts crawl along the underside of the cloud.
Sometimes lightning also leaves the cloud but remains in the sky, a phenomenon that can take many forms. It could jump to another cloud or simply beat the air around the storm if enough charge has built up nearby.
While cloud-based lightning usually doesn't bother people on the surface, it can wreak havoc on our planes, missiles, and other flying machines. Flight paths often take passenger jets straight through major thunderstorms, and while lightning typically passes the outside of the aircraft, it is difficult to fully protect an electrical system in such conditions. In 2009, company officials said Air France Flight 447 was likely to be struck by lightning before disappearing over the Atlantic - it flew into a tropical storm just before the blackout on both electrical systems - although a host of other factors likely compounded it . NASA engineers at Cape Canaveral are also regularly plagued by lightning from Florida's merciless summer thunderstorms, which can delay take-offs and damage expensive equipment.
Lightning out of the blue
Most lightning strikes are negative and fall from the cloud base to the positively charged ground. However, during large thunderstorms, charged positive lightning can leak from the upper regions of the cloud and fly away from the storm before crashing into a distant stretch of negatively charged earth. Sometimes these strikes travel up to 40 km and sneak up on people who don't even know a thunderstorm is nearby - hence the name "lightning out of the blue". Lightning strikes out of the blue are not only stealthy and rare, but also much stronger than normal lightning strikes and therefore cause more physical and property damage.
In May 2019, a woman in Florida accidentally caught this positive lightning bolt. The windows rattled - and they:
Floating current balls have been reported in thunderstorms around the world - and even recreated in a laboratory - but have proven difficult to verify in nature. If there is natural ball lightning, it is fleeting, unpredictable, and rare. Even so, there are tempting clues like the following video that it is real.
Scientists also have a fascinating theory about the nature of ball lightning. For a study published in March 2018, the researchers created a supercooled state of matter called Bose-Einstein condensate and tied its magnetic fields into a complex knot. This created a quantum object called "Shankar Skyrmion" which was theorized more than 40 years ago but has never been successfully created in a laboratory.
A skyrmion is, according to a statement by Amherst University, a "knotted configuration of atomic magnetic moments," essentially a series of interlocking magnetic fields. (As reported by LiveScience, it resembles a collection of connected key rings.) This type of knotted magnetic field is key to the topological theory of ball lightning, as the researchers note, which describes a plasma of hot gas magnetically bounded by the knotted field. Ball lightning can theoretically last much longer than a typical lightning bolt because it is difficult to "loosen" the magnetic knot that holds the plasma in place.
Temporary light events
Lightning isn't the only electrical trick thunderstorms have up their sleeves. There is another world of strange, ghostly lights that most people never see and that dance over storms in the upper atmosphere. They aren't actually lightning bolts in the traditional sense - "transient light events" or "atmospheric optical phenomena" are the preferred terms - but we still don't know much about them.
Sprites are huge flashes of light that occur directly above active thunderstorms and usually correspond to strong, positively charged flashes from cloud to ground. These wispy torches are also known as "red sprites" because most of them glow red. They can shoot up to 60 miles from the cloud cover, although they are weakly charged and rarely last more than a few seconds. The shapes of the sprites have been compared to pillars, carrots, and jellyfish, but their weak charge and soft glow mean they're rarely spotted with the naked eye - in fact, there was no photographic evidence of this until 1989. However, since then thousands of sprites have been photographed and filmed from the ground, from airplanes and from space.
Blue jets are what they sound like: rays of blue energy shooting from the top of a thunderstorm into the surrounding sky. Despite the simple name, they are one of the more mysterious transient light events as they are not directly connected to a cloud-to-ground lightning bolt and are not aligned with the local magnetic field. When the bright blue-and-white stripes emerge from a cloud, they extend upward in narrow cones, gradually fan out, and dissolve at heights of about 30 miles. Blue jets only last a fraction of a second, but have been watched by pilots and even captured on video.
Elves occur like sprites over an area with active cloud-to-ground flashes and also occur in the ionosphere. These glowing, rapidly expanding disks can stretch for 300 miles, but they last for less than a thousandth of a second, which would make them difficult to spot even if there weren't a thunderstorm in your way. NASA discovered Elves in 1992 when a space shuttle's low-light video camera recorded one in action, and scientists believe it was caused by an electromagnetic pulse launched into the ionosphere by a thunderstorm.
For the past 30 years, more Americans have been killed by lightning each year than by hurricanes or tornadoes. However, as deaths are spread over time and distance, this is "the most underestimated weather hazard," according to NOAA. For some reason, many more men die from lightning strikes than women - as of 2006, more than 78 percent of US lightning strikes have been male. In certain parts of the country, particularly Florida, Texas, and other states near the Gulf of Mexico, lightning strikes are more common and severe.
Cloud to ground lightning strikes can attack people in a number of ways. Being outdoors during a thunderstorm - or 30 minutes before or after one - is not a good idea, nor is it near something tall like a tree or a pole. But ideally you should still be inside.
The best place is a building with plumbing and electrical cables as they conduct electricity better than a human body. Structures with exposed openings are unsafe, including sheds, carports, picnic shelters, baseball shelters, and outdoor stadiums. If you're stuck outside, try getting into a closed metal vehicle with the windows up, and avoiding things with open cabins like convertibles, golf carts, tractors, or construction equipment.
Swimming pools are notoriously dangerous during thunderstorms because water conducts electricity so easily. In addition to metal, another top conductor, water can also help lightning strike our homes and businesses, and penetrate through plumbing and electrical systems. The bolt can hit the building directly or run through the power lines and potentially electrocute anyone showering, using a computer, or making a phone call (landlines are the main risk; cell phones are generally safe in a storm). Even if tornadoes are not expected, the safest part of a building is the interior, away from windows, water and electrical appliances.
For more information on lightning science and safety, please visit the following links:
- NOAA: Lightning Basics
- NOAA: Basics of the Thunderstorm
Editor's Note: This story has been updated with new information since it was published in June 2009.
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