forbidden emission line
xat-e gosili-ye bažkam
Fr.: raie d'émission interdite
Fr.: raie interdite
A spectral line emitted by atoms undergoing energy transitions not normally allowed by the → selection rules of → quantum mechanics. Forbidden emission lines form in low-density interstellar gas and are collisionally excited. They are designated by enclosing in brackets, e.g. [O III] and [N II], O and N representing oxygen and nitrogen atoms respectively.
Fr.: transition interdite
Fr.: effet Forbush
A decrease in the Galactic cosmic flux around sunspot maximum as a consequence of Solar flare activity. When sunspots explode, they often hurl massive clouds of hot gas away from the Sun, a phenomenon called → coronal mass ejections (CME). The CMEs contain not only gas but also magnetic fields. So when a CME sweeps past Earth, it also sweeps away many of the electrically-charged cosmic rays.
After Scott E. Forbush, American physicist who studied cosmic rays in the 1930s and 40s; → effect; decrease, from O.Fr. stem of descreistre, from L. decrescere, from → de- "away from" + crescere "to grow."
Kâheš, verbal noun of kâstan, kâhidan "to decrease," from Mid.Pers. kâhitan, kâstan, kâhênitan "to decrease, diminish, lessen;" Av. kasu- "small, little" (Mod.Pers. keh), Proto-Iranian *kas- "to be small, diminish, lessen."
1) The cause of a change in motion or shape of a body.
From O.Fr. force, from L.L. fortia, from neut. pl. of L. fortis "strong," from forctus, from PIE base *bhergh- "high" (cf. Av. barəz- "high, mount," barezan- "height;" O.Pers. baršan- "height;" Mod.Pers. borz in (the mountain chain) Alborz, and borz "height, magnitude," bâlâ "up, above, high, elevated, height," Lori dialect berg "hill, mountain;" Skt. bhrant- "high;" O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg).
Niru, from Mid.Pers. nêrok, Av. nairya- "manly, male" (cf. Skt. nárya-), from nar- "man, male" (Mid./Mod.Pers. nar- "male," Skt. nár- "male").
meydân-e niru (#)
Fr.: champ de force
Same as → field of force.
force multiplier parameter
pârâmun-e bastâgar-e niru
Fr.: paramètre de multiplicateur de force
One of the three quantities (k, α, and δ) which are used in the → radiation-driven wind theory to express the radiation pressure due to spectral lines. These coefficients parametrize the radiation acceleration as: grad≅ k(dv/dr)αge, where ge = σeL/4πcR*2 is the radiative acceleration by electron scattering. The parameter k is dependent on the number of lines that produce the radiation pressure. The parameter α depends on the optical depth of the driving lines and varies between 0 (optically thin) and 1 (optically thick). The parameter δ describes the dependence of k on the density with k ≅ ρδ. The velocity law of radiation-driven winds depends on α and δ, but not on k. The → mass loss rate depends on k, α, and δ (Castor et al. 1975, ApJ 195, 157; Lamers et al., 1995, ApJ 455, 269 and references therein).
Fr.: système de forces
Any set of forces acting on a → rigid body.
force-free magnetic field
Fr.: champ magnétique sans force
The condition in a plasma when the → Lorentz force is zero, that is when the electric current flows along the magnetic field. Force-free magnetic fields are encountered in astrophysical plasmas with negligible gas pressure. The solar corona is the best available example of such fields in action in a plasma.
1) Physics: Caused by an external force.
→ forced oscillation.
Adjective from → force.
Adjective from zur, → strength.
Fr.: écoulement forcé
A fluid flow generated when external forces cause the fluid to flow, for example when a flow is caused by a pump. It contrasts with → free flow.
Fr.: oscillation forcée
The oscillation of a system or object induced by an external periodic force. See also → free oscillation.
The ground or parts situated, or represented as situated, in the front; the portion of a scene or stellar field nearest to the viewer. → background.
From fore, from O.E. fore (prep.) "before, in front of;" (adv.) "before, previously" (cf. O.H.G. fora, Ger. vor, Goth. faiura); from PIE *per-/*pr- (cf. Skt. pura "before, formerly;" Av. paro "before;" Hittite para- "on, forth;" Gk. paros "before," para "from beside, beyond," peri "around, about, toward," pro "before;" L. pro "before, for, instead of," prae "before," per "through, for") + ground, from M.E., from O.E. grund; akin to O.H.G. grunt "ground."
Pišzaminé, from piš- "before; in front," from Mid.Pers. pêš "before, earlier;" O.Pers. paišiya "before; in the presence of" + ziminé "ground," from zamin "earth, ground" → earth.
Fr.: absorption d'avant-plan
Loss of radiant energy received from an astronomical object due to the presence of absorbing matter situated between the object and observer.
M.E., from O.Fr. forest, probably from L.L. forestis (silva) "the outside woods," from L. foris "outside."
Jangal "a wood, forest, a vast land with plenty of trees;" cf. Skt. jangala- "arid , sparingly grown with trees and plants."
došâx, došâxé; cangâl
Fr.: fourche; forchette
1) An instrument having two or more prongs or tines, for holding, lifting, etc.,
as an implement for handling food or any of various agricultural tools (dictionary.com).
Fork, from O.E. forca, from L. furca "pitchfork," of uncertain origin; → mounting.
"two-pronged; fork," from do "two" (Mid.Pers. do, Av. dva-,
Skt. dvi-, Gk. duo, L. duo, E. two, Ger. zwei,
Fr. deux) + šâx "branch; horn," from Mid.Pers. šâk "branch;"
cf. Lith. šaka "branch;" O.S. soxa "plough;" Gothic hoha "plough."
Fr.: monture à fourche
1) dis, disé (#); 2) disidan (#); 3) disândan (#)
Fr.: 1) forme; 2) se former; 3) former
1) (n.) General: The shape and structure of something as distinguished
from its material.
From O.Fr. forme, from L. forma "form, mold, shape, case," origin unknown.
Dis, disé "form, appearance," variants -diz, -diš (tandis
"body form, like a body; effigy;" mâhdis "moon-like;"
šabdiz "night color; a horse of
dark rusty color;" andiš- "to think, contemplate"), from Mid.Pers.
dêsag "form, appearance," dêsidan
"to form, build;" Av. daēs- "to show," daēsa- "sign, omen;"
cf. Skt. deś-
"to show, point out;" PIE *deik- "to show" (cf. Gk. deiknumi "to show,"
dike "manner, custom;" L. dicere "to utter, say;" O.H.G. zeigon,
Ger. zeigen "to show;" O.E. teon "to accuse," tæcan "to teach").
1) According to, or following established or prescribed forms, conventions, etc.
Diseyi, desevar, from dis, → form, + adj. suffixes -i and -var.
Fr.: langage formel
A language designed for use in situations in which natural language is unsuitable, as for example in → mathematics, → logic, or → computer → programming. The symbols and formulas of such languages stand in precisely specified syntactic and semantic relations to one another (Dictionary.com).