1. Coloured rings of lights, typically from blue inside to red outside, that sometimes appear to surround the Sun or Moon. The effect is created by diffraction of light by spherical water drops in such clouds as altocumulus. Compare HALO.
2. Concentric zones of one or more minerals surrounding a core mineral. Coronas can be formed in a number of ways. (a) The discontinuous reaction of minerals with a magma can be preserved as coronas around the original high-temperature mineral if the cooling rate is fast enough to prevent the reactions going to completion. (b) Late-stage fluids may react with an earlier primary mineral to develop a corona of secondary minerals. (c) Two minerals may undergo sub-solidus reactions (reactions occurring after the rock has solidified) to maintain equilibrium as a rock mass cools, developing a corona of lower-temperature minerals. These types of texture are also known as ‘reaction rims’. See also CRYSTAL ZONING.
3. One of the large, circular features (150–600km diameter) of uncertain origin, comprised of up to 10–12 subconcentric ridges and grooves, which surround an inner region of irregular relief, found on the surface of Venus, mainly in a latitudinal belt 55° N–80° N along the borders of Ishtar and Tethus Regio. Most are associated with what appear to be lava flows.
co·ro·na1 / kəˈrōnə/ • n. (pl. -nae / -nē; -nī/ ) 1. Astron. the rarefied gaseous envelope of the sun and other stars. ∎ (also corona discharge) Physics the glow around a conductor at high potential. ∎ a small circle of light seen around the sun or moon, due to diffraction by water droplets. 2. Anat. a crown or crownlike structure. ∎ Bot. the cup-shaped or trumpet-shaped outgrowth at the center of a daffodil or narcissus flower. 3. a circular chandelier in a church. 4. Archit. a part of a cornice having a broad vertical face. co·ro·na2 • n. a long, straight-sided cigar.
corona (in astronomy)
corona, luminous envelope surrounding the sun, outside the chromosphere. Its density is less than one billionth that of the earth's atmosphere. The corona is visible only at the time of totality during a total eclipse of the sun. It then appears as a halo of light with an irregular outer edge, often with streamers radiating from the sun's surface and contrasting with the dark lunar disk that it borders. It is divided into the inner corona, a ring of pale-yellow light against which crimson prominences are outlined, and the outer corona, a pearly white halo that extends far out into space. The corona consists of ionized gas at a temperature of 1 million°C. By means of the coronagraph, the innermost part of the corona can be studied and photographed in full daylight. Although the visible corona extends a few solar radii above the sun, because of its high temperature it produces a continual flow of electrically charged particles called the solar wind that move outward through the solar system.
1. Part of a Classical cornice, called larmier, above the bedmoulding and below the cymatium, with a broad vertical face, usually of considerable projection, with its underside recessed and forming a drip protecting the frieze under it.
2. Circlet or hoop hanging from above, as over an altar: usually carrying candles, it is called a corona lucis, a good example of which survives in Aachen Cathedral.
Corona (city, United States)
Corona (kərō´nə), city (1990 pop. 76,095), Riverside co., S Calif.; inc. 1896. The city developed as a primary citrus fruit producer and shipping center. There is also light manufacturing. The name Corona ( "circle" ) was derived from the 3 mi (5 km) circular drive around the city that was once used for car racing. State prisons for men and women are nearby. Cleveland National Forest and hot springs lie in the vicinity.