| Revision as of 10:38, 9 August 2004 editWilliam M. Connolley (talk | contribs)Autopatrolled, Extended confirmed users, Pending changes reviewers, Rollbackers66,026 edits →Solar irradiance of Earth and its surface: Add atmos para, global dimming link and text. This is not fully reconciled with solar output text.← Previous edit | Latest revision as of 16:19, 14 July 2021 edit undoTom.Reding (talk | contribs)Autopatrolled, Extended confirmed users, Page movers, Template editors3,879,760 editsm +{{Authority control}} (1 ID from Wikidata), WP:GenFixes on (uncategorized page)Tag: AWB | ||
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| '''Solar variation''' refers to fluctuation in the amount of energy emitted by the ]. The Sun is a star undergoing hydrogen to helium fusion reactions due to compression deep inside. The rate of reactions is sufficiently constant that the amount of ] emitted at the surface does not change much. Small variations have been measured from satellites during recent decades. | |||
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| ==Sunspots== | |||
| ]s are relatively dark areas on the surface of the Sun. They have been determined to be cooler than its average surface. However, because they are surrounded by relatively brighter areas, more sunspots means a brighter sun overall. Sunspot number (for which records extend over hundreds of years) can thus be used as a ] for solar output (for which good records only extend for a few decades). | |||
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| ==Solar cycles== | |||
| ]s are cyclic changes in behavior of the Sun. Most obvious is a gradual increase and decrease of the number of sunspots over a period of about 11 years, called the Schwabe cycle. This seems to be due to a shedding of entangled ]s. The Sun's surface is also the most active when there are more sunspots, although the ] does not change much due to an increase in bright spots (]). Other patterns detected are the Hale cycle (22 years) and the Gleissberg cycle (70-100 years). | |||
| ==Solar luminosity== | |||
| The overall brighness of the Sun has been found to vary slightly during a few recent solar cycles. It has been most directly measured by satellites above the atmosphere. Comparisons between ground instruments, high-altitude instruments, and instruments in orbit have been used to calibrate ground instruments. Researchers have combined present readings and factors to adjust historical data. Also used have been proxy data, such as measurements of cosmic ray isotopes to infer solar magnetic activity and thus the likely brightness. | |||
| ==Solar irradiance of Earth and its surface== | |||
| ] is the amount of sunlight which reaches the Earth. The equipment used might measure optical brightness, total radiation, or radiation in various frequencies. Historical estimates use various measurements and proxies. | |||
| There are two common meanings: | |||
| * the radiation reaching the upper atmosphere | |||
| * the radiation reaching some point within the atmosphere, including the surface. | |||
| Various gases within the atmosphere absorb some solar radiation at different wavelengths, and clouds and dust also affect it. Hence measurements above the atmosphere are needed to observe variations in solar output, within the confounding effects of changes to the atmosphere. Indeed, there is some evidence that sunshine at the earths surface has been decreasing in the last 50 years (see ]) possibly caused by increased atmospheric pollution, whilst over roughly the same timespan solar output has been nearly constant. | |||
| ] are computer simulations which are used to examine understanding of climate behavior. Some models use constant values for solar irradiance, while some include the heating effects of a variable Sun. | |||
| ==Other effects due to solar variation== | |||
| Interaction of solar particles, the solar magnetic field, and the Earth's magnetic field, cause variations in the particle and electromagnetic fields at the surface of the planet. Extreme solar events can affect electrical devices. Weakening of the Sun's magnetic field is believed to increase the number of interstellar ] which reach Earth's atmosphere, altering the types of particles reaching the surface. It has been speculated that a change in cosmic rays could cause an increase in certain types of clouds, affecting Earth's ]. | |||
| ==Global warming== | |||
| Some researchers have correlated solar variation with changes in the ]'s average temperature and ] - sometimes finding an effect, and sometimes not. When effects are found they have tended to be greater than can be explained by direct response to the change in radiative forcing from solar change, so some kind of feedback or amplification mechanism is required. See ] for a discussion of attribution of causes of current ]. | |||
| ==Links== | |||
| * The Variable Sun - The American Institute of Physics. http://www.aip.org/history/climate/solar.htm | |||
| * Gerrit Lohmann, Norel Rimbu, Mihai Dima (2004). . International Journal of Climatology 24(8), 1045-1056 - Abstract: http://www.palmod.uni-bremen.de/~gerrit/abstractSolar.html | |||
| * Solar Climatic Effects (Recent Influence) – Summary. ]. ] ]. http://www.co2science.org/subject/s/summaries/solarrecin.htm | |||
| * S.K Solanski, M. Fligge (2001) ESA SP-463, ESA Publications Division. http://www.astro.phys.ethz.ch/papers/fligge/solspa_2.pdf | |||
| * S.K. Solanki, M. Fligge (2000) Space Science Review 94, 127-138 http://www.astro.phys.ethz.ch/papers/fligge/solfli_rev.pdf | |||
| * George C. Reid (1995) Aeronomy Laboratory, NOAA/ERL, Boulder, Colorado. U.S. National Report to IUGG, 1991-1994 Rev. Geophys. Vol. 33 Suppl. http://www.agu.org/revgeophys/reid00/reid00.html | |||
| ] | |||
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