An afterglow in

meteorology Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agricultur ...

consists of several atmospheric optical phenomena, with a general definition as a broad arch of whitish or pinkish

sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

in the

twilight Twilight is daylight illumination produced by diffuse sky radiation when the Sun is below the horizon as sunlight from the upper atmosphere is scattered in a way that illuminates both the Earth's lower atmosphere and also the Earth's surf ...

sky The sky is an unobstructed view upward from the planetary surface, surface of the Earth. It includes the atmosphere of Earth, atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from ...

, consisting of the bright segment and the purple light. Purple light mainly occurs when the Sun is 2–6° below the

horizon The horizon is the apparent curve that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This curve divides all viewing directions based on whethe ...

, from civil to nautical twilight, while the bright segment lasts until the end of the nautical twilight. Afterglow is often in cases of

volcanic eruption A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior h ...

s discussed, while its purple light is discussed as a different particular ''volcanic purple light''. Specifically in volcanic occurrences it is light scattered by fine

particulates Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspension (chemistry), suspended in the atmosphere of Earth, air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate ...

, like

dust Dust is made of particle size, fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian processes, aeolian process), Types of volcan ...

, suspended in the

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

. In the case of alpenglow, which is similar to the Belt of Venus, afterglow is used in general for the golden-red glowing light from the

sunset Sunset (or sundown) is the disappearance of the Sun at the end of the Sun path, below the horizon of the Earth (or any other astronomical object in the Solar System) due to its Earth's rotation, rotation. As viewed from everywhere on Earth, it ...

and sunrise reflected in the sky, and in particularly for its last stage, when the purple light is reflected. The opposite of an afterglow is a foreglow, which occurs before sunrise. Sunlight reaches Earth around civil twilight during golden hour intensely in its low-energy and low-frequency red component. During this part of civil twilight after sunset and before sundawn the red sunlight remains visible by

scattering In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiat ...

through particles in the air. Backscattering, possibly after being reflected off clouds or high snowfields in

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...

regions, furthermore creates a reddish to pinkish light. The high-energy and

high-frequency High frequency (HF) is the International Telecommunication Union, ITU designation for the radio band, band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengt ...

components of light towards blue are scattered out broadly, producing the broader blue light of nautical twilight before or after the reddish light of civil twilight, while in combination with the reddish light producing the purple light. This period of blue dominating is referred to as the blue hour and is, like the golden hour, widely treasured by photographers and painters. After the 1883 eruption of the

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

Krakatoa Krakatoa (), also transcribed (), is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The caldera is part of a volcanic island group (Krakatoa archipelago) comprising four islands. Tw ...

, a remarkable series of red

s appeared worldwide. An enormous amount of exceedingly fine dust were blown to a great height by the volcano's explosion, and then globally diffused by the high atmospheric winds.

Edvard Munch Edvard Munch ( ; ; 12 December 1863 – 23 January 1944) was a Norwegian painter. His 1893 work ''The Scream'' has become one of Western art's most acclaimed images. His childhood was overshadowed by illness, bereavement and the dread of inher ...

's painting '' The Scream'' possibly depicts an afterglow during this period. File:Dämmerung mit Purpurlicht und Schattenstrahlen, 10.10.2011 bei Limburg VIII.jpg, Purple light with crepuscular shadow File:Lamma evening4.jpg, Sunset in Hong Kong after the 1991 eruption of Mount Pinatubo File:Dresden.afterglow.700px.jpg, An afterglow in

Dresden Dresden (; ; Upper Saxon German, Upper Saxon: ''Dräsdn''; , ) is the capital city of the States of Germany, German state of Saxony and its second most populous city after Leipzig. It is the List of cities in Germany by population, 12th most p ...

Saxony Saxony, officially the Free State of Saxony, is a landlocked state of Germany, bordering the states of Brandenburg, Saxony-Anhalt, Thuringia, and Bavaria, as well as the countries of Poland and the Czech Republic. Its capital is Dresden, and ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

File:Afterglow.jpg, An afterglow in

Slovenia Slovenia, officially the Republic of Slovenia, is a country in Central Europe. It borders Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the south and southeast, and a short (46.6 km) coastline within the Adriati ...

n mountains, near Triglav Lakes Valley File:Full Image Sunset Bates College Lewiston Maine July 3 2008 8.30PM.JPG, Sunset over the

Bates College Bates College () is a Private college, private Liberal arts colleges in the United States, liberal arts college in Lewiston, Maine. Anchored by the Historic Quad, the campus of Bates totals with a small urban campus which includes 33 Victorian ...

track in

Lewiston, Maine Lewiston (; ) is the List of municipalities in Maine, second most populous city in the U.S. state of Maine, with the city's population at 37,121 as of the 2020 United States census. The city lies halfway between Augusta, Maine, Augusta, the sta ...

File:Noarlunga Pier, Adelaide.jpg, An afterglow at a pier in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

File:Afterglow in Sanchong, New Taipei 20140114.jpg, An afterglow on skyscrapers in

New Taipei New Taipei City is a Special municipality (Taiwan), special municipality located in regions of Taiwan, northern Taiwan. The city is home to an estimated population of 4,004,367 as of January 2023, making it the most populous city in Taiwan, a ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

File:Afterglow Kraków.JPG, An afterglow on a

Kraków , officially the Royal Capital City of Kraków, is the List of cities and towns in Poland, second-largest and one of the oldest cities in Poland. Situated on the Vistula River in Lesser Poland Voivodeship, the city has a population of 804,237 ...

housing estate File:Optical effect march sunset - NOAA.jpg, Additional to foreglow here refracted sunlight reaches the

South Pole The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the point in the Southern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True South Pole to distinguish ...

just before actual sunrise. At Earth's poles the Sun appears at the horizon only and all day around

equinox A solar equinox is a moment in time when the Sun appears directly above the equator, rather than to its north or south. On the day of the equinox, the Sun appears to rise directly east and set directly west. This occurs twice each year, arou ...

, marking the change between the half year long

polar night Polar night is a phenomenon that occurs in the polar regions of Earth, northernmost and southernmost regions of Earth when the Sun remains below the horizon for more than 24 hours. This only occurs inside the polar circles. The opposite phen ...

and polar day.

References

External links

{{wiktionary Atmospheric optical phenomena es:Arrebol fi:Purppuravalo

See also

References

External links