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| In [[physics]], '''radiative equilibrium''' is the condition where a [[steady state]] system is in [[dynamic equilibrium]], with equal incoming and outgoing [[electromagnetic radiation|radiative]] [[heat flux]] and negligible heat transfer by [[conduction (heat)|conduction]] and [[convection]].<ref name=Modest2013>{{cite book|last=Modest|first=Michael F.|title=Radiative heat transfer|year=2013|publisher=Academic|location=Oxford|isbn=9780123869906|page=298|url=http://books.google.de/books?id=J2KZq0e4lCIC&pg=PA298|edition=3rd ed.}}</ref> In [[atmospheric physics]], under conditions of radiative equilibrium, total flux is constant with depth.<ref name=dePater2010>{{cite book|last=de Pater|first=Imke|title=Planetary sciences|year=2010|publisher=[[Cambridge University Press]]|location=New York|isbn=9780521853712|page=68|url=http://books.google.de/books?id=a_ijoTgDhnEC&pg=PA68|edition=2nd ed.|coauthors=Lissauer, Jack J.}}</ref> In [[astrophysics]], radiative equilibrium is used to determine atmospheric radiation of [[star]]s. In [[climate science]], the net change in the [[tropopause]] after temperatures readjust to radiative equilibrium in the [[stratosphere]], is used to determine the [[radiative forcing]], as part of an assessment of natural and anthropogenic climate change.<ref>{{Cite book
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| |author=IPCC
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| | title = Climate Change 2007: Working Group I: The Physical Science Basis
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| | publisher = Cambridge University Press
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| | year = 2007
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| | chapter = 2.2 Concept of Radiative Forcing
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| | chapterurl = http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-2.html
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| }}</ref>
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| ==Definitions==
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| ===History===
| | They're always ready to help, and they're always making changes to the site to make sure you won't have troubles in the first place. Medical word press themes give you the latest medical designs. I thought about what would happen by placing a text widget in the sidebar beneath my banner ad, and so it went. Word - Press also provides protection against spamming, as security is a measure issue. Also our developers are well convergent with the latest technologies and bitty-gritty of wordpress website design and promises to deliver you the best solution that you can ever have. <br><br>If you have any sort of inquiries concerning where and just how to use [http://ps4.vg/wordpress_dropbox_backup_343826 wordpress backup], you can call us at the web site. Word - Press is known as the most popular blogging platform all over the web and is used by millions of blog enthusiasts worldwide. Wordpress have every reason with it which promote wordpress development. It sorts the results of a search according to category, tags and comments. t need to use the back button or the URL to get to your home page. Aided by the completely foolproof j - Query color selector, you're able to change the colors of factors of your theme a the click on the screen, with very little previous web site design experience. <br><br>Just ensure that you hire experienced Word - Press CMS developer who is experienced enough to perform the task of Word - Press customization to get optimum benefits of Word - Press CMS. Word - Press has ensured the users of this open source blogging platform do not have to troubleshoot on their own, or seek outside help. You can now search through the thousands of available plugins to add all kinds of functionality to your Word - Press site. You or your web designer can customize it as per your specific needs. There are plenty of tables that are attached to this particular database. <br><br>There has been a huge increase in the number of developers releasing free premium Word - Press themes over the years. Cameras with a pentaprism (as in comparison to pentamirror) ensure that little mild is lost before it strikes your eye, however these often increase the cost of the digital camera considerably. However, you may not be able to find a theme that is in sync with your business. It supports backup scheduling and allows you to either download the backup file or email it to you. Make sure you have the latest versions of all your plugins are updated. <br><br>Internet is not only the source for information, it is also one of the source for passive income. Visit our website to learn more about how you can benefit. This allows updates to be sent anyone who wants them via an RSS reader or directly to their email. In addition, Word - Press design integration is also possible. Customers within a few seconds after visiting a site form their opinion about the site. |
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| In 1791 [[Pierre Prevost]] showed that all bodies radiate heat and concluded, ''Radiation will exactly compensate absorption''. He used the terms absolute and relative equilibrium to describe changes.<ref name="Prevost 1791">[http://books.google.fr/books?id=7ZLOAAAAMAAJ&pg=PA314&lpg=PA314#v=onepage&q&f=false Prevost, P. (1791). Mémoire sur l'equilibre du feu. ''Journal de Physique'' (Paris), vol 38 pp. 314–322.]</ref> Prevost considered that what is nowadays called the [[photon gas]] or [[electromagnetic radiation]] was a fluid that he called "free heat" ({{lang-fr|le feu}}). Prevost proposed that free radiant heat is a very rare fluid, rays of which, like light rays, pass through each other without detectable disturbance of their passage. Prevost's called his theory ''movable equilibrium of heat'', now designated as the theory of exchanges, which stated that each body radiates to, and receives radiation from, other bodies. The radiation from each body is emitted regardless of the presence or absence of other bodies.<ref>{{cite book |last=Maxwell |first=J.C. | year=1871 |title=Theory of Heat| publisher=Longmans, Green and Co, London | pages = 221–222 |url=[http://archive.org/details/theoryofheat00maxwrich Abstract][http://ia700504.us.archive.org/6/items/theoryofheat00maxwrich/theoryofheat00maxwrich.pdf PDF]}}</ref><ref>{{cite book |last= |first= | year=1901 |title=The Laws of Radiation and Absorption: Memoirs by Prévost, Stewart, Kirchhoff, Bunsen| publisher=American Book Company |url=[http://archive.org/details/lawsradiationan00bunsgoog Abstract][http://archive.org/stream/lawsofradiationa00bracrich/lawsofradiationa00bracrich_djvu.txt Full Text]}}</ref><ref>Partington, J.R. (1949). ''An Advanced Treatise on Physical Chemistry'', volume 1, ''Fundamental Principles. The Properties of Gases'', Longmans, Green and Co, London, p. 467.</ref>
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| In 1906 [[Karl Schwarzschild]] postulated the radiative equilibrium (German: ''Strahlungsgleichgewicht'') dependent on [[Kirchhoff's law of thermal radiation]], when he studied the sun.<ref>Schwarzschild, K. (1906). Über das Gleichgewicht der Sonnenatmosphäre.[https://eudml.org/doc/58631 Download PDF]</ref>
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| ===Pointwise radiative equilibrium===
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| Following [[Max Planck|Planck]] (1914),<ref name="Planck 1914"/> a radiative field is often described in terms of [[specific radiative intensity]], which is a function of each geometrical point in a space region, at an instant of time.<ref name="Mihalas Mihalas 1984">[http://www.filestube.com/9c5b2744807c2c3d03e9/details.html Mihalas, D., Weibel-Mihalas, B. (1984). ''Foundations of Radiation Hydrodynamics'', Oxford University Press, New York, ISBN 0-19-503437-6.]</ref><ref name="Goody Yung 1989">Goody, R.M., Yung, Y.L. (1989). ''Atmospheric Radiation. Theoretical Basis'', second edition, Oxford University Press, New York, 1989, ISBN 0-19-505134-3.</ref> A detailed definition is given by Goody and Yung (1989).<ref name="Goody Yung 1989"/> They think of the interconversion between thermal radiation and heat in matter. From the specific radiative intensity they derive <math>\mathbf{F}_\nu</math>, the monochromatic vector flux density of radiation at each point in a region of space, which is equal to the time averaged monochromatic [[Poynting vector]] at that point (Mihalas 1978<ref name="Mihalas 1978">Mihalas, D. (1978). ''Stellar Atmospheres'', 2nd edition, Freeman, San Francisco, ISBN 0-7167-0359-9.</ref> on pages 9–11). They define the monochromatic volume-specific rate of gain of heat by matter from radiation as the negative of the divergence of the monochromatic flux density vector; it is a scalar function of the position of the point:
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| ::: <math>h_\nu = - \nabla \cdot \mathbf{F}_\nu</math>.
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| They define '''(pointwise) monochromatic radiative equilibrium''' by
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| ::: <math>\nabla \cdot \mathbf{F}_\nu = 0 </math> at every point of the region that is in radiative equilibrium.
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| They define '''(pointwise) radiative equilibrium''' by
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| :::<math>h = \int_0^{\infty} h_\nu d\nu = 0</math> at every point of the region that is in radiative equilibrium.
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| This means that, at every point of the region of space that is in (pointwise) radiative equilibrium, the total, for all frequencies of radiation, interconversion of energy between thermal radiation and energy content in matter is nil.
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| ====Approximate pointwise radiative equilibrium====
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| [[Subrahmanyan Chandrasekhar|Chandrasekhar]] (1950, p. 290)<ref>Chandrasekhar, S. (1950). ''Radiative Transfer'', Oxford University Press, Oxford, 1950.</ref> writes of a model of a [[stellar atmosphere]] in which "there are no mechanisms, other than radiation, for transporting heat within the atmosphere ... [and] there are no sources of heat in the atmosphere." This is hardly different from Schwarzschild's 1906 approximate concept, but is more precisely stated.
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| === Exchange equilibrium between systems===
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| {{see also|Thermodynamic equilibrium #Relation of exchange equilibrium between systems}}
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| Radiative exchange equilibrium occurs with thermodynamic systems. [[Max Planck|Planck]] (1914)<ref name="Planck 1914">Planck, M. (1914). ''The Theory of Heat Radiation'' p. 40</ref> refers to a condition of [[thermodynamic equilibrium]], in which "any two bodies or elements of bodies selected at random exchange by radiation equal amounts of heat with each other."
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| The term '''radiative exchange equilibrium''' can also be used to refer to two specified regions of space that exchange equal amounts of radiation by emission and absorption (even when the steady state is not one of thermodynamic equilibrium, but is one in which some sub-processes include net transport of matter or energy including radiation).
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| ==Radiative equilibrium in astrophysics==
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| Radiative equilibrium for a [[star]], is taken as a whole and not confining attention only to its atmosphere. And when the rate of heat transfer from nuclear reactions plus [[viscosity]] to the microscopic motions of the material particles of the star is ''balanced'' by the transfer of energy by electromagnetic radiation from the star to space.
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| A star that is radiating energy to space cannot be in a steady state of temperature distribution unless there is a steady supply of energy from nuclear reactions within the star, to support the radiation to space.<ref name="Cox 1968">Cox, J.P. with Giuli, R.T. (1968, reprint 1984). ''Principles of Stellar Structure'', Gordon and Breach, New York, ISBN 0-677-01950-5, p. 134.</ref>
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| [[Planetary equilibrium temperature]] is the theoretical temperature for a [[blackbody]], which does not consider a radiative atmosphere.
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| ==Radiative equilibrium in Earth sciences==
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| {{see also|Earth's radiation balance}}
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| '''Radiative equilibrium''' or '''radiative balance''' or just '''energy balance''', describe a [[steady state]] net change of [[infrared]] radiation from Earth and [[shortwave radiation]] from [[outer space]].
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| ==See also==
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| * [[Earth's energy budget]]
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| * [[Earth's radiation balance]]
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| * [[Non-equilibrium thermodynamics]]
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| * [[Planetary equilibrium temperature]]
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| * [[Thermal equilibrium]]
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| * [[Thermodynamic equilibrium]]
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| ==References==
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| <references/>
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| [[Category:Thermodynamics]]
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