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.
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) = I0e-μx, where I(x) is the intensity at depth of x cm and I0 is the original intensity.
Fr.: facteur d'atténuation
The ratio of the radiation intensity after traversing a layer of matter to its intensity before.
Position of a satellite with respect to the horizon or some other fixed reference plane.
Fr., from It. attitudine "disposition, posture," from L.L. aptitudo "faculty."
Ruykard, noun from ruy kardan "to turn the face toward,"
from ruy "face"
(Mid.Pers. rôy, rôdh "face," Av. raoδa-
"growth," in plural "appearance," from raod- "to grow, sprout, shoot,"
cf. Skt. róha- "rising, height") + kardan "to do, make, perform"
(Mid.Pers. kardan, O.Pers./Av. kar- "to do, make, build,"
Av. kərənaoiti "makes," cf. Skt. kr- "to do, to make,"
krnoti "makes," karma "act, deed;" PIE base kwer-
"to do, to make").
A prefix meaning 10-18.
From Danish or Norwegian atten "eighteen," from O.N. attjan "eighteen," from atta "eight" (compare with Gk. okto, L. octo, Skt. astau, Av. ašta-, Mod.Pers. hašt; PIE *okt(u)) + tjan "ten" (compare with Skt. dasa, Av. dasa, Mod.Pers. dah, Gk. deka, L. decem; PIE *dekm).
To cause to draw near or adhere by physical force.
L. attractus, p.p. of attrahere "to draw, to attract," from ad- "to" + trahere "to pull, draw."
Darkašidan, from dar- "in, into" + kašidan "to draw, attract," → galaxy.
The act or capability of attracting. A physical force (gravitational, electric, magnetic, etc.) exerted by material bodies.
Attraction, n. from → attract.
Having the quality of attracting.
Verbal adj. from → attract.
Fr.: force attractive
The physical body that attracts. → Great Attractor.
1, 2) âbâž, âbâžé; 3) âbâžidan
Fr.: 1, 2) attribut; 3) attribuer
1) General: Something attributed as belonging to a person, thing, or group;
a quality, characteristic, or property.
Âbâž, âbâžé, from â- strength or nuance prefix + bâž "tribute, toll, impost," → distribute.
A type of → achondrite meteorite composed mostly of the magnesium silicate mineral → enstatite (Mg2Si2O6). The group is named for the small Aubres → meteorite that fell near Nyons, France, on Sep. 14, 1836. Outside Antarctica only about 10 aubrites are known, mostly the result of witnessed falls. Aubrites make up only 0.14% of all known meteorites in our terrestrial meteorite collection.
From Fr. Aubres, a commune in the Drôme department in southeastern France; + → -ite.
The Charioteer. A conspicuous northern constellation lying midway between → Perseus and → Ursa Major and in a region crossed by the → Milky Way. The brightest star is → Capella. Auriga is the site of the Galactic → anticenter. Abbreviation: Aur; genitive form: Aurigae.
L. auriga "a charioteer, driver," from aureæ "bridle of a horse" + agere "set in motion, drive, lead."
Arrâberân "charioteer," from arrâbé "chariot, cart"
+ rân "driver," from rândan "to drive."
Arrâbé probably from *arâba, from *râba,
from *râda, compare with Av. ratha- "chariot," akin to
Skt. rathah "car, chariot," L. rota "wheel,"
rotare "revolve, roll,"
Lith. ratas "wheel,"
O.H.G. rad, Ger. Rad, Du. rad,
O.Ir. roth; PIE *roto- "to run, to turn, to roll."
A phenomenon consisting of luminous colorful arcs, rays, and streamers that appear in the Earth's upper atmosphere during the night with the greatest frequency in the northern and southern polar magnetic zones. This → non-thermal radiation is caused by the emission of light from atoms excited by electrons accelerated along the planet's magnetic field lines at the magnetic poles. Fluorescent emission from atomic oxygen at 5557 Å results in a greenish glow, and there is a weaker effect from the red line at 6300 Å. Blue and purple colors are emitted by atomic and molecular nitrogen.
L. Aurora, the Roman goddess of dawn, akin to Av. uš-, ušah- "dawn," Skt. usas-, usah- "dawn," Gk. eos "dawn," Lith. ausra "dawn," O.E. east "east," PIE *ausus- "dawn," from *aus- "to shine."
Ušé, from Av. uš-, ušah-, as above.
Fr.: aurore australe
The aurora in the Southern hemisphere, also called as Southern Lights.
Fr.: aurore boréale
The aurora in the Northern hemisphere, also called as Northern Lights.
Pertaining to the → aurora phenomenon.
Fr.: émission aurorale
Fr.: raie aurorale
1) A prominent → forbidden line in the spectra of
the aurora at wavelengths of 5577 and 6300 Å giving the aurora its characteristic green and
Both are emitted by atomic oxygen, the former in its transition from the
second lowest excited electronic state (1S) to the lowest
excited electronic state (1D), the latter in its transition
from the lowest excited electronic state (1D) to the atomic
ground state (3P).
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.