The induced separation of charge in pure liquid water has been known since the 1840s as has the electrification of pure liquid water by the tribo-electric effect. 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. 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). This part of the thunderstorm cloud is called the anvil. The 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. 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. The upper part of the thunderstorm cloud becomes positively charged while the middle to the lower part of the thunderstorm cloud becomes negatively charged. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air. The updraft carries the super-cooled cloud droplets and very small ice crystals upward. In that area, the combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 ☌ (5 to −13 ☏) see Figure 1. Uncharged, colliding water-drops can become charged because of charge transfer between them (as aqueous ions) in an electric field as would exist in a thunder cloud. Electrification can be by the triboelectric effect as a result of ion transfer between colliding bodies. The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. (Figure 1) The main charging area in a thunderstorm occurs in the central part of the storm where the air is moving upward rapidly (updraft) and temperatures range from −15 to −25 ☌ (5 to −13 ☏). The first surviving photograph is from 1882, by William Nicholson Jennings, a photographer who spent half his life capturing pictures of lightning and proving its diversity. The first known photograph of lightning is from 1847, by Thomas Martin Easterly. The fear of lightning is called astraphobia. At all times people have been fascinated by the sight and difference of lightning. Idiomatic expressions derived from lightning, such as the English expression "bolt from the blue", are common across languages. Humans have deified lightning for millennia. Many other observational variants are recognized, including " heat lightning", which can be seen from a great distance but not heard dry lightning, which can cause forest fires and ball lightning, which is rarely observed scientifically. The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud (intra-cloud), between two clouds (cloud-to-cloud), or between a cloud and the ground (cloud-to-ground), in which case it is referred to as a lightning strike. Lightning is an atmospheric electrical phenomenon and contributes to the global atmospheric electrical circuit. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions. Lightning causes thunder, a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. This discharge may produce a wide range of electromagnetic radiation, from heat created by the rapid movement of electrons, to brilliant flashes of visible light in the form of black-body radiation. Lightning is a natural phenomenon formed by the occurrence of lightning bolts, which are electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or with one in the atmosphere and on the ground, temporarily neutralizing these in an almost instantaneous release of an average of one gigajoule of energy.
0 Comments
Leave a Reply. |