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.
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.
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.
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.
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).
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).
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.
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.
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.
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.
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.
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.
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.
Fr.: vent induit par raie
Same as → radiation-driven wind.
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
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 I→ O stars. See also → wind momentum.
Fr.: fenêtre optique
The optical portion of the electromagnetic spectrum that passes through the atmosphere all the way to the ground.
optically thick wind
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.
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.
pulsar wind nebula (PWN)
miq-e bâd-e pulsâr, ~ ~ tapâr
Fr.: nébuleuse de vent de pulsar
Same as → plerion.