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Main article: Distribution of lightning Data from space-based sensors reveal the uneven distribution of worldwide lightning strikes. Units: flashes/km2/yr. Data obtained from April 1995 to February 2003 from NASA's Optical Transient Detector and from January 1998 to February 2003 from NASA's Lightning Imaging Sensor.
As a result of their greater power, positive lightning strikes are considerably more dangerous than negative strikes. Positive lightning produces both higher peak currents and longer continuing currents, making them capable of heating surfaces to much higher levels which increases the likelihood of a fire being ignited. The long distances positive lightning can propagate through clear air explains why they are known as "bolts from the blue", giving no warning to observers. Ball lightning may be an atmospheric electrical phenomenon, the physical nature of which is still controversial. The term refers to reports of luminous, usually spherical objects which vary from pea-sized to several metres in diameter. [84] It is sometimes associated with thunderstorms, but unlike lightning flashes, which last only a fraction of a second, ball lightning reportedly lasts many seconds. Ball lightning has been described by eyewitnesses but rarely recorded by meteorologists. [85] [86] Scientific data on natural ball lightning is scarce owing to its infrequency and unpredictability. The presumption of its existence is based on reported public sightings, and has therefore produced somewhat inconsistent findings. Brett Porter, [87] a wildlife ranger, reported taking a photo in Queensland, Australia in 1987.a b Lu, Gaopeng; Cummer, Steven A; Blakeslee, Richard J; Weiss, Stephanie; Beasley, William H (2012). "Lightning morphology and impulse charge moment change of high peak current negative strokes". Journal of Geophysical Research: Atmospheres. 117 (D4): n/a. Bibcode: 2012JGRD..117.4212L. CiteSeerX 10.1.1.308.9842. doi: 10.1029/2011JD016890. Lightning on Venus has been a controversial subject after decades of study. During the Soviet Venera and U.S. Pioneer missions of the 1970s and 1980s, signals suggesting lightning may be present in the upper atmosphere were detected. [129] The short Cassini–Huygens mission fly-by of Venus in 1999 detected no signs of lightning, but radio pulses recorded by the spacecraft Venus Express (which began orbiting Venus in April 2006) may originate from lightning on Venus. [130] Human-related phenomena
NASA Dataset Information". NASA. 2007. Archived from the original on September 15, 2007 . Retrieved September 11, 2007. There are variations of each type, such as "positive" versus "negative" CG flashes, that have different physical characteristics common to each which can be measured. Different common names used to describe a particular lightning event may be attributed to the same or to different events. Upward lightning or ground-to-cloud lightning is a lightning flash which originates from the top of a grounded object and propagates upward from this point. This type of lightning can be triggered by a preceding lightning flash, or it may initiate entirely on its own. The former is generally found in regions where spider lightning occurs, and may involve multiple grounded objects simultaneously. [105] The latter usually occurs during the cold season and may be the dominant lightning type in thundersnow events. [106] The Path of Least Resistance". July 2001. Archived from the original on January 4, 2016 . Retrieved January 9, 2016. Cloud-to-ground (CG) lightning is either positive or negative, as defined by the direction of the conventional electric current between cloud and ground. Most CG lightning is negative, meaning that a negative charge is transferred to ground and electrons travel downward along the lightning channel (conventionally the current flows from the ground to the cloud). The reverse happens in a positive CG flash, where electrons travel upward along the lightning channel and a positive charge is transferred to the ground (conventionally the current flows from the cloud to the ground). Positive lightning is less common than negative lightning, and on average makes up less than 5% of all lightning strikes. [73] A bolt from the blue lightning strike which appears to initiate from the clear, but the turbulent sky above the anvil cloud and drive a bolt of plasma through the cloud directly to the ground. They are commonly referred to as positive flashes, despite the fact that they are usually negative in polarity.
6. Lightning destroys trees
The Earth-ionosphere waveguide traps electromagnetic VLF- and ELF waves. Electromagnetic pulses transmitted by lightning strikes propagate within that waveguide. The waveguide is dispersive, which means that their group velocity depends on frequency. The difference of the group time delay of a lightning pulse at adjacent frequencies is proportional to the distance between transmitter and receiver. Together with direction-finding methods, this allows locating lightning strikes up to distances of 10,000km from their origin. Moreover, the eigenfrequencies of the Earth-ionospheric waveguide, the Schumann resonances
Turman, B. N. (1977). "Detection of lightning superbolts". Journal of Geophysical Research. 82 (18): 2566–2568. Bibcode: 1977JGR....82.2566T. doi: 10.1029/JC082i018p02566. Bruning, Eric C.; Tillier, Clemens E.; Edgington, Samantha F.; Rudlosky, Scott D.; Zajic, Joe; Gravelle, Chad; Foster, Matt; Calhoun, Kristin M.; Campbell, P. Adrian; Stano, Geoffrey T.; Schultz, ChristopherThe upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from the thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures. [15] Although rare, lightning can also travel from one cloud to another (or more!). Spider lightning refers to long, horizontal moving flashes often seen on the underside of stratiform clouds. (Not to be confused with intracloud lightning within a single cloud). Marshall, Tim; David Hoadley (illustrator) (May 1995). Storm Talk. Texas. {{ cite book}}: CS1 maint: location missing publisher ( link) Small, short duration sparks, recently documented near newly extruded magma, attest to the material being highly charged prior to even entering the atmosphere. [124]
The electric current of the return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 100,000km/s (one-third of the speed of light). [64]Robinson, Dan. "Weather Library: Lightning Types & Classifications". Archived from the original on February 15, 2013 . Retrieved March 17, 2013. Staying Safe in Lightning Alley". NASA. January 3, 2007. Archived from the original on July 13, 2007 . Retrieved September 24, 2007. The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. [15]
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