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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solar constant
  پایای ِ خورشیدی   
pâypa-ye xoršidi (#)

Fr.: constante solaire   

The amount of solar radiation in all wavelengths received per unit of time per unit of area on a theoretical surface perpendicular to the Sun's rays and at Earth's mean distance from the Sun. Its mean value is 1367.7 W m-2 or 1.37 × 106 erg sec-1 cm-2. In other words, the solar constant is the mean → solar irradiance on the outer atmosphere when the Sun and Earth are spaced at 1 → astronomical unit. See also: → solar luminosity.

solar; → constant.

solar corona
  هورتاج، تاج ِ خورشیدی   
hurtâj, tâj-e xoršid (#)

Fr.: couronne solaire   

The outermost atmosphere of the Sun immediately above the → chromosphere, which can be seen during a total solar eclipse. It consists of hot (1-2 × 106 K), extremely tenuous gas (about 10-16 g cm-3) extending for millions of kilometer from the Sun's surface.

solar; → corona.

solar depression
  نشیب ِ خورشید   
nešib-e xoršid

Fr.: dépression solaire   

The → angle between the → sea horizon, the → center of → Earth, and the center of the → solar disk.

solar; → depression.

solar equation
  هموگش ِ خورشیدی   
hamugeš-e xoršidi

Fr.: équation solaire   

In ancient astronomy, the difference between the Sun's mean and actual position. The ancients observed that, although the motion of the Sun in the ecliptic is almost uniform, it is subject to a small annual variation.

solar; → equation.

solar longitude
  درژنای ِ خورشیدی   
derežnâ-ye xoršidi

Fr.: longitude du Soleil   

The ecliptic longitude of the Sun. It varies from 0° (at the vernal equinox) to 360° during the year. By Kepler's Second Law, the rate of change of the solar longitude is such that the Earth sweeps out equal areas on the ecliptic plane in equal times.

solar; → longitude.

solar radiation
  تابش ِ خورشیدی   
tâbeš-e xoršidi

Fr.: rayonnement solaire   

All the constituents making up the Sun's emission: photons, electrons, protons, neutrinos, and atomic nuclei.

solar; → radiation.

solar radiation pressure
  فشار ِ تابش ِ خورشید   
fešâr-e tâbeš xoršid (#)

Fr.: pression du rayonnement solaire   

The → radiation pressure of solar photons, which pushes a comet's dust outward to form a → dust tail.

solar; → radiation; → pressure.

solar rotation
  چرخش ِ خورشید   
carxeš-e xoršid (#)

Fr.: rotation du Soleil   

The motion of the Sun around an axis which is roughly perpendicular to the plane of the → ecliptic; the Sun's rotational axis is tilted by 7.25° from perpendicular to the ecliptic. It rotates in the → counterclockwise direction (when viewed from the north), the same direction that the planets rotate (and orbit around the Sun). The Sun's rotation is differential, i.e. the period varies with latitude on the Sun (→ differential rotation). Equatorial regions rotate in about 25.6 days. The regions at 60 degrees latitude rotate more slowly, in about 30.9 days.

solar; → rotation.

Solberg-Hoiland criterion
  سنجیدار ِ سولبرگ-هویلاند   
sanjidâr-e Solberg-Høiland

Fr.: critère de Solberg-Høiland   

A criterion for → convective stability in → massive stars. The Solberg-Høiland stability criterion corresponds to the inclusion of the effect of → rotation (variation of → centrifugal force) in the convective stability criterion. It is a combination of → Ledoux's criterion (or possibly → Schwarzschild's criterion) and → Rayleigh's criterion. Both the dynamical shear and Solberg-Høiland instabilities occur in the case of a very large → angular velocity decrease outwards. Therefore, in a → rotating star the Ledoux or Schwarzschild criteria for convective instability should be replaced by the Solberg-Høiland criterion. More specifically, this criterion accounts for the difference of the centrifugal force for an adiabatically displaced fluid element. It is also known as the axisymmetric baroclinic instability. It arises when the net force (gravity + buoyancy + centrifugal force) applied to a fluid parcel in an adiabatical displacement has components only in the direction of the displacement (A. Maeder, Physics, Formation and Evolution of Rotating Stars, 2009, Springer).

E. Høiland, 1939, On the Interpretation and Application of the Circulation Theorems of V. Bjerknes. Archiv for mathematik og naturvidenskab. B. XLII. Nr. 5. Oslo.
H. Solberg, 1936 (reprint), Le mouvement d'inertie de l'atmosphere stable et son rôle dans la théorie des cyclones.
H. Solberg, 1941, On the Stability of the Circular Vortex. Avhandl. utg. av Det Norske Videnskaps-Akademi i Oslo. I. Mat-Naturv. Klasse. No. 11.
Wasiutynski, J. 1946, Astrophysica Norvegica, 4, 1.

solidification
  دفزش؛ دفزانش   
dafzeš; dafzâneš

Fr.: solidification   

1) To become or make solid, hard, or firm.

solid; → -fy.

soliton
  سولیتون   
soliton

Fr.: soliton   

Math., Physics: A solution of a certain type of partial differential equation that represents a solitary wave. A soliton is a self-reinforcing wave that maintains its shape while it travels at constant speed. Solitons are caused by a cancellation of nonlinear and dispersive effects in the medium.

From solit(ary) + → -on.

solution
  لویش   
luyeš

Fr.: solution   

1) The act of solving a problem, question. The state of being solved.
2a) Math.: The process of determining the answer to a problem. The answer itself.
2b) Math.: Of a differential equation, any function which, when put into the equation, converts it into an identity.
3) Chem.: The process by which a gas, liquid, or solid is dispersed homogeneously in a gas, liquid, or solid without chemical change. a homogeneous, molecular mixture of two or more substances.

Verbal noun of → solve.

solvation
  لویه   
luyé

Fr.: solvation   

Any of a class of chemical reactions in which solute and solvent molecules combine.

From solv(ent), → solvent + -ation.

Luyé, from luy- the stem of luyidésolute and luyandésolvent + nuance suffix.

sonde
  گمانه   
gomâné

Fr.: sonde   

A rocket or balloon carrying instruments to probe conditions in the upper atmosphere.

From Fr. sonde "ounding line; plumb line."

Gomâné "a shaft sunk in order to ascertain the depth of the water when making a subterraneous canal," from Proto-Iranian *vi-mā-, from vi- "apart, away from, out" (cf. Av. vi-; O.Pers. viy- "apart, away;" Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + mā- "to measure" (cf. O.Pers./Av. mā(y)- "to measure;" Mod.Pers. mâ/mun/mân "measure," as in Pers. terms âz- "to test;" pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl;" PIE base *me- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum).

sonic
  صدایی   
sedâyi (#)

Fr.: sonique   

Of, relating to, or being the speed of sound in a medium.

From L. sonus, → sound.

Sedâyi, pertaining to sedâ, → sound.

sonic boom
  غریو ِ صدا   
qariv-e sedâ (#)

Fr.: bang sonique   

A noise caused by a shock wave that emanates from an object traveling at or above the speed of sound.

sonic; boom, M.E. bombon, bummyn "to buzz;" cf. Du. bommen, Ger. bummen, word made by sound imitation.

Qariv "shout, clamour, cry;" sedâyi, → sonic.

sonic point
  نقطه‌ی ِ صدایی   
noqte-ye sedâyi

Fr.: point sonique   

The point where the → stellar wind makes a transition from → subsonic to → supersonic flow. In the particular case of a spherically symmetric wind (thus with no magnetic field), the distance from star, at which the sonic point occurs, is given by: rs = (GM*)/2cs2, where G is the → gravitational constant, M* is the stellar mass, and cs the → sound speed at the sonic point.

sonic; → point.

sorption
  شمش   
šameš

Fr.: sorption   

The process of sorbing. The state of being sorbed. → absorption; → adsorption.

Verbal noun of → sorb

sound horizon
  افق ِ صدا   
ofoq-e sedâ

Fr.: horizon sonore   

The maximum distance a → sound wave could have traveled through the ionized plasma from the → Big Bang until the → recombination era. It is 150 → Mpc, or bout 500 million → light-years. Sound horizon is the equivalent of the concept of → cosmic horizon, where one replaces → electromagnetic wave by → sound wave. The sound horizon is a fixed physical scale at the → last scattering surface. Cosmological models relate the value of sound horizon to the angle it subtends on the sky today. Same as acoustic horizon and sonic horizon. See also → CMB angular power spectrum.

sound; → horizon.

sounding balloon
  بالون ِ گمانه‌زنی   
bâlon-e gamâne-zani

Fr.: ballon-sonde   

A small, free balloon sent into the upper atmosphere to measure, record, and transmit meteorological reports to a ground station.

sounding; → balloon.

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