An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < age rad win > >>

Number of Results: 45 Search : wind
ageostrophic wind
  باد ِ نازمین‌چرخشی   
bâd-e nâ-zamincarxeši

Fr.: vent agéostrophique   

Meteo.: The wind component deviating from the → geostrophic wind in the absence of the → geostrophic balance. In other words, ageostrophic wind is the difference between the true wind and the geostrophic wind.

From negation prefix → a- + → geostrophic; → wind.

atmospheric windows
  روزنه‌های ِ جوی   
rowzanehâ-ye javvi (#)

Fr.: fenêtres atmosphériques   

Gaps in → atmospheric absorption, allowing a range of electromagnetic wavelengths to pass through the atmosphere and reach the Earth.

atmospheric; → window.

Baade's window
  روزنه‌ی ِ باده   
rowzane-ye Baade

Fr.: fenêtre de Baade   

An area of the sky with relatively low amounts of  → interstellar dust along the → line of sight, occurring toward the  → constellation of  → Sagittarius, near the → globular cluster NGC 6522. The window, through which stars in the → Galactic bulge are visible, lies 3.9 degrees south of the → Galactic center, corresponding to a line of sight that passes within 1,800 → light-years of the → Milky Way's core. It is named after Walter Baade, who used it to observe → RR Lyrae stars  in the → Galactic bulge region. 

Baade-Wesselink method; → window.

clumped wind
  باد ِ گوده‌دار   
bâd-e gudedâr

Fr.: vent grumelé   

A → radiation-driven wind of → Wolf-Rayet and → O stars, which is not homogeneous, and contains compressions and rarefactions in the form of density clumps. Observationally, wind clumping appears as moving, small-scale structures in spectral line profiles. Indirect indicators of wind clumping include: electron scattering wings of emission lines, too-weak observed UV line profiles, and shapes of X-ray lines. The most likely physical explanation for the presence of these clumps is an instability in radiatively-driven winds. The inclusion of a clumping factor in the models of W-R winds reduces the → mass loss rates by a factor ~ 2-4 relative to homogeneous models. See also → clumping factor.

clumpy; → wind.

continuum-driven wind
  باد ِ پیوستار‌زاد   
bâd-e peyvastârzâd

Fr.: vent induit par continuum   

The transfer of photon momentum to free electrons. The acceleration by → continuum emission can be given by: ac = (σ/m)(L*/4πR2c), where σ is the → Thomson scattering  → cross section, m is the mass per free electron, L* is → stellar luminosity, R* is radius, and c the → speed of light. The ratio of ac to the → surface gravity is ≅ 2 × 10-5L*/M*, with M* and L* in solar units. The atmosphere is is stable if ac very smaller than ggrav. If L* is above the → Eddington limit, the radiation pressure in the continuum leads to very heavy → mass loss and thus to expanding envelopes (K.S. de Boer & W. Seggewiss, 2008, Stars and Stellar Evolution, EDP Sciences).

continuum; → drive; → wind.

disk wind
  باد ِ گرده   
bâd-e gerdé

Fr.: vent de disque   

In → magnetocentrifugal models of → protostars, the wind arising from a significant range of radii in the → accretion disk. The contribution from innermost parts of the disk is dealt with by the → X-wind model. (Königl A. and Pudritz R. E., 2000, In Protostars and Planets IV, V. Mannings, et al. (eds.), Tucson: Univ. Arizona Press, p. 759).

disk; → wind.

dust-driven wind
  باد ِ غبار‌زاد   
bâd-e qobârzâd

Fr.: vent induit par poussière   

A → stellar wind generated by the action of → radiation pressure on dust grains. This occurs in the case of cool stars, such as → AGB stars, with → effective temperatures below 2500 K when the density is sufficiently large. Since dust is a very good continuum absorber, the dust grains will be radiatively accelerated outward.

dust; → drive; → wind.

equatorial wind
  باد ِ هموگاری   
bâd-e hamugâri

Fr.: vent équatorial   

A slow, dense → stellar wind (high → mass loss rate) emanating from equatorial regions of a → B[e] star. The equatorial and → polar winds are the two main wind components in B[e] stars. The mechanism suggested to explain this wind morphology is the rotationally induced → bistability mechanism.

equatorial; → wind.

galactic wind
  باد ِ کهکشانی   
bâd-e kahkašâni

Fr.: vent galactique   

An outflow of hot gas, analogous to the → solar wind, from a galaxy that has recently undergone a high → burst of star formation or has an → active galactic nucleus. Galactic winds are streams of high speed charged particles blowing out of galaxies with speeds of 300 to 3,000 km s-1. In the case of starbursts, galactic winds are powered by → stellar winds driven by → massive stars and → supernova explosions. Galactic winds contain a mixture of extremely hot metal-enriched supernova ejecta and cooler entrained gas and dust. Outflowing material has been observed at great distances from galaxies (10 to 100 kpc). In some cases they escape the galaxy potential well and pollute the → intergalactic medium with → heavy elements. A prominent example is the → superwind of the starburst galaxy M82.

galactic; → wind.

Galactic windows
  روزنه‌های ِ کهکشان   
rowzanehâ-ye kahkešân

Fr.: fenêtres galactiques   

The regions near the Galactic plane where there is low absorption of light by interstellar clouds so that some external galaxies may be seen through them.

galactic; → window.

geostrophic wind
  باد ِ زمین‌چرخشی   
bâd-e zamincarxeši

Fr.: vent géostrophique   

Meteo.: A wind which is balanced by the → Coriolis effect and → pressure gradient force. An air parcel initially at rest will move from high pressure to low pressure because of the pressure gradient force. However, the air parcel in its movement is deflected by the Coriolis force, to the right in the northern hemisphere and to the left on the southern hemisphere. As the wind gains speed, the deflection increases until the Coriolis force equals the pressure gradient force. At this point, the wind will be blowing parallel to the → isobars.

geostrophic; → wind.

infrared window
  روزنه‌ی ِ فروسرخ   
rowzane-ye forusorx (#)

Fr.: fenêtre infrarouge   

A range of infrared wavelengths to which the Earth's atmosphere is relatively transparent, and at which observations can be made from the ground. Infrared windows are found near wavelengths of 1.25, 1.65, 2.2, 3.6, 5.0, 10, 20, and 30 microns, and beyond 300 microns.

infrared; → window.

isothermal wind
  باد ِ ایزودما   
bâd-e izodamâ

Fr.: vent isotherme   

A → stellar wind in which the gas is subject to only two forces: the inward directed gravity and the outward directed gradient of the gas pressure.

isothermal; → wind.

line-driven wind
  باد ِ خط‌زاد   
bâd-e xattzâd

Fr.: vent induit par raie   

Same as → radiation-driven wind.

line; → drive; → wind.

mechanical wind
  باد ِ مکانیکی   
bâd-e mekâniki

Fr.: vent mécanique   

A process in which matter is shed into a → Keplerian disk from a star rotating at the → critical velocity. The disk is probably destroyed by the pressure exerted by the stellar radiation and finally matter is lost. Such a process seems to occur around → Be stars which are stars rotating at or very near the critical limit (Meynet et al. 2007, arXiv:0709.2275).

mechanical; → wind.

modified wind momentum
  جنباک ِ باد ِ واترزیده   
jonbâk-e bâd-e vâtarzidé

Fr.: moment angulaire de vent modifié   

A quantity defined as Π = (dM/dt) v R0.5 for a star with radius R having a wind with → terminal velocity v and a → mass loss rate dM/dt. There is a tight linear relation between the modified wind momenta and the stellar luminosities for → Population IO stars. See also → wind momentum.

modify; → wind; → momentum.

optical window
  روزنه‌یِ نوری   
rowzane-ye nuri

Fr.: fenêtre optique   

The optical portion of the electromagnetic spectrum that passes through the atmosphere all the way to the ground.

optical; → window.

optically thick wind
  باد ِ نورانه ستبر   
bâd-e nurâné setabr

Fr.: vent optiquement épais   

A wind with the → sonic point located at large optical depth for continuum. In particular, → Wolf-Rayet star winds are → optically thick. However, the outer parts of W-R winds are → optically thin for continuum, and in those regions the matter flow is driven by the same mechanism as in the winds of OB stars.

optically; → thick; → wind.

polar wind
  باد ِ قطبی   
bâd-e qotbi

Fr.: vent polaire   

1) The → solar wind occurring at high latitudes during low → solar activity as a fast (around 750 km s-1) and relatively steady flow. A remarkable feature of the polar wind is the ubiquitous presence of an intense flow of → Alfvénic fluctuations.
2) One of the two main wind components in → B[e] stars. The pole is hotter than the equator due to the → gravity darkening effect leading to a relatively fast, low-density wind driven by Fe IV lines. The other component is the → equatorial wind. The mechanism put forward to explain this wind morphology is the rotationally induced → bistability mechanism.
3) An extremely cold wind blowing from the north or south polar regions of the Earth.

polar; → wind.

pulsar wind nebula (PWN)
  میغ ِ باد ِ پولسار، ~ ~ تپار   
miq-e bâd-e pulsâr, ~ ~ tapâr

Fr.: nébuleuse de vent de pulsar   

Same as → plerion.

pulsar; → wind; → nebula.

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