An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1234
Coriolis effect
  اسکر ِ کوریولیس   
oskar-e Koriolis

Fr.: effet Coriolis   

The apparent → deflection of a body in motion with respect to the Earth, as seen by an → observer on the Earth, caused by the → Earth's rotation. Thus, a projectile fired due north from any point on the northern hemisphere will land slightly east of its target (deflection to the right). This involves two factors: 1) the eastward velocity of Earth's surface decreases from the → equator to the → poles, and 2) when an object starts to move north or south without being firmly connected to the ground it maintains its initial eastward speed (conservation of → angular momentum). Hence, an object travelling away from the equator will be heading east faster than the ground and will seem to be forced east. On the other hand, a ball fired in the northern hemisphere toward the equator deflects to the west. As for the southern hemisphere, a ball fired southward will deflect East. The projectile is not subject to this effect only on the equator, when it is thrown in an east-west direction. The Coriolis effect is therefore greater at higher → latitudes and smaller near the equator. This effect is of paramount importance to the large-scale → atmospheric circulation, the development of storms, and the sea-breeze circulation. In low pressure systems, i.e. zones where air ascends, the air is less dense than its surroundings and this creates a center of low atmospheric pressure. Winds blow from areas of high pressure to areas of low pressure, and so the surface winds would tend to blow toward a low pressure center. But, because of the Coriolis effect, they are deflected. In the northern hemisphere they are deflected toward the right, and fail to arrive at the low pressure center, but instead circulate around it → counterclockwise. In the southern hemisphere the circulation around a low pressure center would be → clockwise. Regarding high pressure systems in the northern hemisphere, a general clockwise rotation is created around the center. Same as the → Coriolis force. See also → geostrophic wind, → geostrophic flow.

Named after Gaspard Gustave Coriolis (1792-1843), French engineer and mathematician who first described this effect; → effect.

Coriolis force
  نیروی ِ کوریولیس   
niru-ye Coriolis (#)

Fr.: force de Coriolis   

An apparent, rather than real, force exerted on a body when it moves in a rotating → reference frame. Same as the → Coriolis effect.

Coriolis effect; → force.

Coriolis frequency
  بسامد ِ کوریولیس   
basâmad-e Coriolis

Fr.: fréquence de Coriolis   

A quantity defined as f = 2ω.sinθ, where ω is the Earth's → angular velocity, 2π/T, T is the rotation period of the Earth (→ sidereal day), and θ is the → latitude. Also called the → Coriolis parameter. This frequency occurs often in oceanographic studies. If an → iceberg is floating in a frictionless sea, and is given a push and allowed to move freely, it will travel in a circle of radius U/f, where U is the initial speed imparted by the push. This circle is called an inertial circle.

Coriolis effect; → frequency.

Coriolis theorem
  فربین ِ کوریولیس   
farbin-e Coriolis

Fr.: théorème de Coriolis   

The → absolute acceleration of a point P, which is moving with respect to a local → reference frame that is also in motion, is equal to the vector sum of:
a) the acceleration P would have if it were fixed to the moving system;
b) the acceleration of P with respect to the local moving system; and
c) a compound supplementary → Coriolis acceleration.

Coriolis effect; → theorem.

Cornu prism
  منشور ِ کورنو   
manšur-s Cornu (#)

Fr.: prisme de Cornu   

A combination of two 30° prisms, one of left-handed quartz and the other of right-handed quartz. The prisms are cemented together in order to get a 60° prism. The device will correct for light rotation and will transmit the beam in a straight direction. The Cornu prism has good ultraviolet transmitting qualities and no → double refraction.

Cornu's spiral; → prism.

Cornu's spiral
  مارپیچ ِ کورنو   
mârpic-e Cornu (#)

Fr.: spirale de Cornu   

A plane curve whose Cartesian coordinates are given in parametric form by the → Fresnel integrals. Cornu's spiral is an auxiliary tool for calculating the Fresnel integrals. It is particularly used for the calculation of the diffraction of light at the straight edge of a flat screen or at a straight slit. It is characterized by the fact that the angle it makes with the abscissa axis is proportional to the square of the distance along the curve from the origin of coordinates. Cornu's spiral comprises two branches, symmetrical with respect to the origin and winding asymptotically on the points (0.5,0.5) and (-0.5,-0.5) respectively. Also known as the → clothoid or Euler's spiral.

Named after the French physicist Alfred Cornu (1841-1902); → spiral.


Fr.: corollaire   

A natural outcome of a → theorem.

L.L. corollarium "a deduction, consequence," from L. corollarium, originally "money paid for a garland," hence "gift, gratuity, something extra;" from corolla "small garland," diminutive of → corona.

Pasâné, from pasân "after," from pas "after, afterward; consequently," variant pošt; Mid.Pers. pas "after; behind, before;" O.Pers. pasā "after;" Av. pasca "afterward (of time); then; behind (of space);" cf. Skt. paścā "after, later, behind;" L. post "after, afterward; behind, in the rear;" O.C.S. po "after, behind;" Lith. pas "at, by;" PIE *pos-, *posko-, + nunace suffix

  تاج، هورتاج   
tâj, hurtâj (#)

Fr.: couronne   

1) 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.
2) Meteorology: A set of one or more colored rings of small radii, concentrically surrounding the disk of the Sun, Moon, or other luminary when veiled by a thin cloud.

L. corona "crown, garland," cf. Gk. korone "anything curved, kind of crown."

Tâj "crown," loanword in Arm. tag "crown," tagavor "king," Proto-Iranian *tâgâ-, maybe from PIE base *(s)teg- "to cover" (L. toga "a garment worn by male citizens in ancient Rome;" hurtâj, from hur, → sun, + tâj.

Corona Australis
  تاج ِ هودری، ~ شمالی   
tâj-e hudari, šomâli

Fr.: Couronne australe   

The Southern Crown. A small, faint southern → constellation, also called Corona Austrini. Abbreviation: CrA, genitive: Coronae Australis.

corona; L. australis "southern."

Corona Borealis
  تاج ِ دشتری، ~ جنوبی   
tâj-e daštari, ~ jonubi

Fr.: Couronne boréale   

The Northern Crown. A small but prominent northern → constellation that lies east of → Arcturus, between → Boötes and → Hercules, and comprises a distinctive arc formed by the stars seven stars. Abbreviation: CrB; genitive: Coronae Borealis.

corona; L. borealis "northern."

  هورتاجنگار، تاجنگار   
hurtâjnegâr (#), tâjnegâr (#)

Fr.: coronographe   

An instrument which, when used in a telescope, produces an artificial eclipse, permitting the study of the → solar corona without a total eclipse of the Sun. It was invented in 1930 by the French astronomer Bernard Lyot (1897-1952).

From → corona + → -graph.

  تاجی، هورتاجی   
tâji (#), hurtâji (#)

Fr.: coronal   

Of or relating to a → corona.

Adj., from → corona + → -al.

coronal condensation
  چگالش ِ تاجی   
cagâleš-e tâji

Fr.: condensation coronale   

A part of the → solar corona where the gas density and the temperature are higher than in its vicinity. The coronal condensations are visible on the solar limb, above → sunspot groups. Images in X-rays and those supplied by → coronagraphs in white light reveal that such condensations consist of structures in the form of nodes, underlining the corona magnetic field (M.S.: SDE).

coronal; → condensation.

coronal features
  آرنگ‌های ِ هورتاجی   
âranghâ-ye hurtâji

Fr.: motifs coronaux   

Several phenomena occurring in the Sun's corona, such as a → helmet streamer, → polar plume, → coronal loop, → coronal hole.

coronal; → feature.

coronal gas
  گاز ِ تاجی   
gâz-e tâji

Fr.: gaz coronal   

A component of the → interstellar medium in the Galaxy which appears as pockets of gas at temperatures of over one million degrees, but extremely low densities of 104 atoms per cubic centimeter. The hot coronal gas is believed to be material blown out of violent supernova explosions. It is called "coronal gas", after a similarity with the hot gas in → solar corona.

coronal; → gas.

coronal hole
  سوراخ ِ هورتاجی   
surâx-e hurtâji

Fr.: trou coronal   

An area in the → solar corona which appears dark in X-rays and ultraviolet light. The gas density in these areas are very low, about 100 times less than that of coronal → active regions. The magnetic field lines in a coronal hole extend out into → interplanetary space rather than returning to the Sun's surface, as they do in other parts of the Sun (→ open magnetic field line). Ionized hot gas can escape easily along such a path, and this brings about high speed → solar wind streams.

coronal; → hole.

coronal line
  خط ِ هورتاجی   
xatt-e hurtâji

Fr.: raie coronale   

An → emission line in the spectrum of the → solar corona caused by highly ionized metal ions; especially those of iron, such as the red and green lines at 6375 Å and 5303 Å [Fe X] (Fe9+ ion) and [Fe XIV] (Fe13+ ion), respectively. From their discovery in 1870 until 1939, it was believed that these → forbidden lines would be due to an unknown element, called → coronium. Ultraviolet and X-ray coronal lines are also detectable in stars.

coronal; → line.

coronal loop
  گردال ِ هورتاجی   
gerdâl-e hurtâj

Fr.: boucle coronale   

An arc-like structure in the Sun's → corona that is found around → sunspots and in → active regions. These structures are associated with the closed magnetic field lines that connect magnetic regions on the solar surface. The loops are sometimes as high as 10,000 km with their two ends situated in photosphere regions of opposite magnetic polarity. This implies that the coronal loops are tubes of magnetic flux filled with hot plasma. They last for days or weeks but most change quite rapidly.

coronal; → loop.

coronal mass ejection (CME)
  اشانش ِ جرم از هورتاج   
ešâneš-e jerm az hurtâj

Fr.: éjection de masse coronale   

A huge eruption of material from regions of the solar corona in which the magnetic field is closed, but which suffer an extremely energetic disruption. Over the course of several hours up to 10,000 billion kg of this material is ejected into → interplanetary space with a a speed of as high as 3000 km/s. CMEs are most spectacularly observed by a white light coronagraph located outside Earth's atmosphere. Such observations from Skylab in the early 1970's were the first to reveal this phenomenon. CME's disrupt the flow of the → solar wind and can produce intense electromagnetic disturbances that can severely damage satellites and disrupt power grids on Earth. When these ejections reach the Earth, they give rise to → geomagnetic storms. The frequency varies with the → solar cycle; during solar minimum they come at a rate of about one per week, and during maximum there is an average of about two or three per day. See also → interplanetary coronal mass ejections (ICME).

coronal; → mass; → ejection.

coronal rain
  باران ِ هورتاجی   
bârân-e hurtâji

Fr.: pluie coronale   

Material that condenses in the Sun's corona and appears to rain down into the chromosphere, as observed at the solar limb above strong sunspots.

coronal; → rain.

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