XV International Conference on Atmospheric Electricity, 15–20, June 2014. It is easier to study scientifically because it terminates on a physical object, namely the Earth, and lends itself to being measured by instruments on the ground. Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. A build up of positive charge builds up on the ground beneath the cloud, attracted to the negative charge in the bottom of the cloud. Where the lightning current path passes through rock, soil, or metal these materials can become permanently magnetized. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above the ground and tops up to 15 km (9.3 mi) in height. As lightning travels through sandy soil, the soil surrounding the plasma channel may melt, forming tubular structures called fulgurites. Lightning is an electrical discharge caused by imbalances between storm clouds and the ground, or within the clouds themselves.  The lighting detection data can be converted into a real-time map of lightning activity across the Western Hemisphere; this mapping technique has been implemented by the United States National Weather Service. The most vivid crawler behavior occurs in well developed thunderstorms that feature extensive rear anvil shearing. Most lightning happens inside a cloud, but sometimes it happens between the cloud and the ground. At certain times of the year, lightning bugs will fly high up into the clouds. This effect is known as lightning-induced remanent magnetism, or LIRM. When the lowermost step comes within 150 feet (46 meters) of a positively charged object, it is met by a climbing surge of positive electricity, called a streamer, which can rise up through a building, a tree, or even a person. , Since recoil and dart leader processes do not occur on negative leaders, subsequent return strokes very seldom utilize the same channel on positive ground flashes which are explained later in the article.. The bolt of lightning in heraldry is called a thunderbolt and is shown as a zigzag with non-pointed ends. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel) develops a negative charge. The surge current is inversely related to the Surge impedance ... so the higher in impedance, then the lower the current. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. This increases the total bundle surface area in inverse proportion to the individual strand radius, for a fixed total cross-sectional area. This symbol usually represents power and speed. Due to the extensive solid material (ash) content, unlike the water rich charge generating zones of a normal thundercloud, it is often called a dirty thunderstorm. , Researchers at the University of Florida found that the final one-dimensional speeds of 10 flashes observed were between 1.0×105 and 1.4×106 m/s, with an average of 4.4×105 m/s.. Although in the minority on Earth, superbolts appear to be common on Jupiter. The radiated pulses rapidly weaken as their distance from the origin increases. Lightning streaks inside a cloud, between clouds, and from clouds to the ground. 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).  In the traditional religion of the African Bantu tribes, lightning is a sign of the ire of the gods. The earliest detector invented to warn of the approach of a thunderstorm was the lightning bell. A lightning bolt is also the NATO symbol for a signal asset. , Starting in 2016, the National Oceanic and Atmospheric Administration launched Geostationary Operational Environmental Satellite–R Series (GOES-R) weather satellites outfitted with Geostationary Lightning Mapper (GLM) instruments which are near-infrared optical transient detectors that can detect the momentary changes in an optical scene, indicating the presence of lightning. Newitz, A. This article incorporates public domain material from the National Oceanic and Atmospheric Administration document: "Understanding Lightning: Thunderstorm Electrification".