sunspot

sunspot
sunspotted, adj.sunspottedness, n.
/sun"spot'/, n.
one of the relatively dark patches that appear periodically on the surface of the sun and affect terrestrial magnetism and certain other terrestrial phenomena.
[1805-15; SUN + SPOT]

* * *

Cooler-than-average region of gas on the Sun's surface associated with strong local magnetic activity.

Sunspots appear as dark spots, but only in contrast with the surrounding photosphere, which is several thousand degrees hotter. Spots several times larger than Earth are visible to the unaided eye (viewed through a filter); very small ones are hard to see even with a telescope. They come and go as part of the solar cycle, usually in pairs or groups, and may last for months; their cause appears to be related to the magnetic field reversals that occur every 11 years. The reality of these apparent flaws in the Sun was generally accepted only с 1611. Periods of high sunspot activity are associated on Earth with brighter auroras and interference with radio signals.

* * *

      vortex of gas on the surface of the Sun associated with strong local magnetic activity. Spots look dark only by contrast with the surrounding photosphere, which is several thousand degrees hotter. The dark centre of a spot is called the umbra; the outer, lighter ring, the penumbra. Spots may be several times larger than the Earth or so small that telescopic observation is difficult. They may last for months. Single spots do appear, but most are in pairs or groups, with the members of a pair (leader and follower in respect to the direction of the Sun's rotation) having opposite magnetic polarity. This polarity reverses from one solar cycle to the next; i.e., if leaders in one cycle are north magnetic poles, leaders in the succeeding cycle will be south poles. Leaders and followers in one hemisphere of the Sun are almost always opposite in polarity from their counterparts across the equator.

      Some large spots are visible to the unaided eye when the Sun is seen through clouds or in a camera-obscura image. But general acceptance of the reality of these apparent flaws in the Sun came only about 1611, when systematic study was begun independently by Galileo, Thomas Harriot, Johannes Fabricius, and Christoph Scheiner. S.H. Schwabe (Schwabe, Samuel Heinrich) in 1843 announced discovery of the solar cycle, in which the number of spots reaches a maximum about every 11 years on the average, as do the effects of solar disturbances (e.g., auroras) on the Earth.

      By observing spots, R.C. Carrington (Carrington, Richard Christopher) found (c. 1860) that the Sun rotates not as a solid body but differentially, fastest at the equator. Sunspots are never seen exactly at the equator or near the poles. Vilhelm Bjerknes theorized in 1926 that spots are the erupting ends of magnetic vortices broken by the Sun's differential rotation. Various elaborations on this idea have been proposed, but the cause of sunspots is still uncertain. George Ellery Hale in 1908 discovered their magnetic fields; John Evershed in 1909 detected the radial motion of gas away from sunspot centres. Annie Russel Maunder in 1922 charted the latitude drift of spots during each solar cycle. Her chart is sometimes called the butterfly diagram because of the winglike shapes assumed by the graph. Each solar cycle begins with small spots appearing in middle latitudes of the Sun. Succeeding spots appear progressively closer to the Sun's equator as the cycle reaches its maximum level of activity and declines.

* * *


Universalium. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • sunspot — 1868, in astronomy, from SUN (Cf. sun) + SPOT (Cf. spot). Earlier “a spot on the skin caused by exposure to the sun” (1818) …   Etymology dictionary

  • sunspot — ► NOUN Astronomy ▪ a temporary darker and cooler patch on the sun s surface, associated with the sun s magnetic field …   English terms dictionary

  • sunspot — [sun′spät΄] n. any of the temporarily cooler regions appearing cyclically as dark spots on the surface of the sun, accompanied by increased geomagnetic disturbances …   English World dictionary

  • Sunspot — A sunspot is a region on the Sun s surface (photosphere) that is marked by intense magnetic activity, which inhibits convection, forming areas of reduced surface temperature. They can be visible from Earth without the aid of a telescope. Although …   Wikipedia

  • Sunspot — In economics, sunspots are extrinsic random variables upon which participants coordinate their decisions. Extrinsic random variables do not affect economic fundamentals directly, but may have an effect on equilibrium outcomes because they… …   Investment dictionary

  • sunspot — UK [ˈsʌnˌspɒt] / US [ˈsʌnˌspɑt] noun [countable] Word forms sunspot : singular sunspot plural sunspots 1) science a dark area on the surface of the sun 2) a very sunny place that is popular for holidays …   English dictionary

  • sunspot — /ˈsʌnspɒt / (say sunspot) noun 1. one of the relatively dark patches which appear periodically on the surface of the sun, and which have a certain effect on terrestrial magnetism and other terrestrial phenomena. Their appearance is spasmodic but… …  

  • Sunspot — Tache solaire Taches solaires Une tache solaire (anglais : sunspot) est une région sur la surface du Soleil (photosphère) qui est marquée par une température inférieure à son environnement et a une intense activité magnétique, qui inhibe la …   Wikipédia en Français

  • sunspot — Saulės dėmė statusas T sritis fizika atitikmenys: angl. sunspot vok. Sonnenfleck, m rus. солнечное пятно, n pranc. tache solaire, f …   Fizikos terminų žodynas

  • sunspot maximum — sunspot maximum, the period during the sunspot cycle in which sunspots are most frequent …   Useful english dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”