An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 3079 Search : on
atmospheric circulation
  پرهونش ِ هواسپهری   
parhuneš-e havâsepehri

Fr.: circulation atmosphérique   

The large-scale movements of air around areas of high and low pressure whereby heat is distributed on the surface of the Earth. Atmospheric motion is driven by uneven heating of the planet. The atmosphere (and ocean) → transfers the excess heat from → tropics to → poles. The flow is determined by balance between → pressure gradients and the → Coriolis effect.

atmospheric; → circulation.

atmospheric dispersion
  پاشش ِ جوی   
pâšeš-e javvi

Fr.: dispersion atmosphérique   

The splitting of starlight into a spectrum in the atmosphere because the atmosphere acts as a refracting prism. This phenomenon brings about a practical problem for spectroscopic observations using a slit. → differential refraction; → atmospheric refraction.

atmospheric; → dispersion.

atmospheric emission
  گسیل ِ جوی   
gosil-e javvi

Fr.: émission atmosphérique   

The emission of electromagnetic radiation from the atmosphere due to thermal and → non-thermal processes. → Thermal emission comes mainly from → water vapor. Non-thermal processes result in emission lines oxygen (optical) and OH (near-IR). Atmospheric emission is a very significant source of noise in astronomical observations. See also → airglow, → aurora.

atmospheric; → emission.

atmospheric extinction
  خاموشی ِ جوی   
xâmuši-ye javvi

Fr.: extinction atmosphérique   

The decrease in the intensity of light from a celestial body due to absorption and scattering by Earth's atmosphere. It increases from the zenith to the horizon and affects short wavelengths more than long wavelengths, so that objects near the horizon appear redder than they do at the zenith.

atmospheric; → extinction.

atmospheric muon
  موءون ِ جوی، ~ هواسپهری   
muon-e javvi, ~ havâsepehri

Fr.: muon atmosphérique   

A → subatomic particle produced when → primary cosmic rays, impinge on the Earth's atmosphere producing a particle cascade, in which secondary particles decay into → muons. In the energy range up to 100 → GeV atmospheric muons come mostly from the decay of secondary → pions: π±→ μ± + anti-νμ. At higher energies, the → kaon contribution to the muon flux become significant, reaching the asymptotic value of 27% at about 10 TeV: K±→ μ± + anti-νμ.

atmospheric; → muon.

atmospheric refraction
  شکست ِ جوی   
šekast-e javvi

Fr.: réfraction atmosphérique   

The shift in apparent direction of a celestial object caused by the bending of light while passing through the Earth's atmosphere. Since the density of the atmosphere decreases with altitude, the starlight will bend more as it continues down through the atmosphere. As a result, a star will appear higher in the sky than its true direction.

atmospheric; → refraction.

atomic diffusion
  پخش ِ اتمی   
paxš-e atomi

Fr.: diffusion atomique   

element diffusion.

atomic; → diffusion.

atomic proposition
  گزاره‌ی ِ اتمی   
gozâre-ye atomi

Fr.: proposition atomique   

In → propositional logic, a → sentence without any → connectives. See also → molecular proposition.

atomic; → proposition.

atomic transition
  گذرش ِ اتمی   
gozareš-e atomi

Fr.: transition atomique   

A change in the → energy level or → state of an → atom in which a → quantum of energy is either gained or lost. See also → forbidden transition; → permitted transition; → semiforbidden transition.

atomic; → transition.

attention
  آتانش   
âtâneš

Fr.: attention   

1) The act or faculty of attending, especially by directing the mind to an object.
2) Observant care; consideration (Dictionary.com).

attend; → -tion.

attenuation
  تنکش   
tonokeš (#)

Fr.: atténuation   

The falling off of the energy density of radiation with distance from the source, or with passage through an absorbing or scattering medium.

Verbal noun of → attenuate.

attenuation coefficient
  همگر ِ تنکش   
hamgar-e tonokeš

Fr.: coefficient d'bsorption   

The fraction of a beam of → X-rays or → gamma rays that is absorbed or scattered per unit thickness of the → absorber. The linear attenuation coefficient, denoted by the symbol μ, appears in the equation I(x) = I0ex, where I(x) is the intensity at depth of x cm and I0 is the original intensity.

attenuation; → coefficient.

attenuation factor
  کروند ِ تنکش   
karvand-e tonokeš

Fr.: facteur d'atténuation   

The ratio of the radiation intensity after traversing a layer of matter to its intensity before.

attenuation; → factor.

attraction
  درکشش   
darkašeš

Fr.: attraction   

The act or capability of attracting. A physical force (gravitational, electric, magnetic, etc.) exerted by material bodies.

Attraction, n. from → attract.

attribution
  آباژش   
âbâžeš

Fr.: attribution   

1) The act of attributing.
2) Something attributed.

Verbal noun of → attribute.

Auger electron
  الکترون ِ اژه   
elektron-e Auger

Fr.: électron d'Auger   

An electron that is emitted when an electron from a higher → energy level falls into a → vacancy in an inner shell, according to the → Auger-Meitner effect. The process usually occurs when the atom is bombarded with high energy electrons. If the collision ejects an inner-shell electron, an electron from a higher level will quickly drop to this lower level to fill the vacancy. Most of the time, the energy is released in the form of a photon. But sometimes the energy is transferred to another electron, which is ejected from the atom.

Auger-Meitner effect; → electron.

auroral emission
  گسیل ِ اوشه‌ای   
gosil-e uše-yi

Fr.: émission aurorale   

The → electromagnetic radiation emitted in planetary atmospheres involving the → aurora phenomenon.

auroral; → emission.

auroral zone
  زنار ِ اوشه‌ای   
zonâr-e uše-yi

Fr.: zone aurorale   

A roughly circular band around either geomagnetic pole above which there is a maximum of auroral activity. It lies about 10 to 15° of geomagnetic latitude from the geomagnetic poles.

auroral; → zone.

authentication
  راستین‌شماری، راستین‌آزمایی   
râstinšomâri, râstin-âzmâyi

Fr.: authentification   

Computers: The process by which a user's identity is checked within the network to ensure that the user has access to the requested resources.

Verbal noun of → authenticate.

autocorrelation
  خودهم‌باز‌آنش   
xod-hambâzâneš

Fr.: autocorrélation   

1) In radio astronomy, a process performed by an → autocorrelator.
2) In statistics, a linear relation between values of a random variable over time.
3) In electronics, a technique used to detect cyclic activity in a complex signal.

Autocorrelation, from → auto- "self" + → correlation.

Xod-hambâzâneš, from xod- "self" + hambâzâneš, → correlation.

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