An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 683
magnetic reversal
  وارونش ِ مغناتیسی   
vâruneš-e meqnâtisi

Fr.: inversion magnétique   

A change in the Earth's → magnetic field in which the → magnetic north pole is transformed into a → magnetic south pole and the magnetic south pole becomes a magnetic north pole. There are geological proofs indicating that the Earth's magnetic field has undergone numerous reversals of → polarity in the past. In the last 10 million years, there have been, on average, 4 or 5 reversals per million years. At other times, for example during the → Cretaceous era, there have been much longer periods when no reversals occurred. Over the past two centuries, Earth's magnetic field has weakened by 15%. Risks of a weak magnetic field include more deaths from cancer due to increased radiation, electrical grid collapse from severe solar storms, climate change, and temporary ozone holes.

magnetic; → reversal.

magnetic Reynolds number
  عدد ِ رینولدز ِ مغناتیسی   
adad-e Reynolds-e meqnâtisi

Fr.: nombre de Reynolds magnétique   

A → dimensionless quantity used in → magnetohydrodynamics to describe the relative balance of → magnetic advection to → magnetic diffusion. It is given by: Rm = σμ0νLU0, where σ is the → conductivity of the fluid, μ0 is the → magnetic permeability of the fluid, L is he characteristic length scale of the fluid flow, and U0 the characteristic velocity of the flow. A typical value for the Earth is Rm ~ 200.

magnetic; → Reynolds number.

magnetic rigidity
  سخت‌پایی ِ مغناتیسی   
saxtpâyi-ye meqnâtisi

Fr.: rigidité magnétique   

In → plasma physics, a → quantity that describes the → resistance of a → charged particle to change its direction of motion under the influence of a perpendicular → magnetic field. Rigidity is defined as: R = rLBc = (pc)/(Ze), where rL is the → Larmor radius, B is → magnetic induction, c is the → speed of light, p is the → momentum of the particle, Z is → atomic number, and e the → electron charge. Since pc has the dimensions of energy and e the dimensions of charge, rigidity has the dimensions of → volts (a 10 GeV proton has a rigidity of 10 GV). In → cosmic ray studies, the energies of cosmic rays are often quoted in terms of their rigidities, rather than their energies per nucleon.

magnetic; → rigidity.

magnetic south pole
  قطب ِ دشتر ِ مغناتیسی   
qotab-e daštar-e meqnâtisi

Fr.: pôle sud magnétique   

The → counterpart of the → magnetic north pole. It lies near the → geographic north pole.

magnetic; → south; → pole.

magnetic star
  ستاره‌ی ِ مغناتیسی   
setâre-ye meqnâtisi (#)

Fr.: étoile magnétique   

A star (usually of spectral type A) with strong integrated magnetic field ranging up to 30,000 gauss.

magnetic; → star.

magnetic storm
  توفان ِ مغناتیسی   
tufân-e meqnâtisi (#)

Fr.: orage magnétique   

A temporary, worldwide disturbance of the Earth's magnetic field by streams of charged particles from the Sun. Magnetic storms are frequently characterized by a sudden onset, in which the magnetic field undergoes marked changes in the course of an hour or less, followed by a very gradual return to normalcy, which may take several days.

magnetic; → storm.

magnetic susceptibility
  برخودگیری ِ مغناتیسی   
barxodgiri-ye meqnêtisi

Fr.: susceptibilité magnétique   

A property of material defined by the ratio of the → magnetization to the → magnetic intensity. In other words, the magnetization per unit magnetic intensity.

magnetic; → susceptibility.

magnetic tape
  نوار ِ مغناتیسی   
navâr-e meqnâtisi

Fr.: bande magnétique   

A continuous, flexible ribbon impregnated or coated with magnetic-sensitive material on which information (sound, images, data, etc.) may be recorded.

magnetic; → tape.

magnetic vector potential
  توند ِ برداری ِ مغناتیسی   
tavand-e bordâri-ye meqnâtisi

Fr.: vecteur potentiel magnétique   

A vector field A defined so that the → magnetic field  B is given by its → curl: B = ∇ x A.

magnetic; → vector; → potential.

magnetic-dipole radiation
  تابش ِ دوقطبه‌ی ِ مغناتیسی   
tâbeš-e doqotbe-ye meqnâtisi (#)

Fr.: rayonnement du dipôle magnétique   

Radiation emitted by a rotating magnet.

magnetic; → dipole; → radiation.


Fr.: magnétisme   

The study of magnetic phenomena, comprising magnetostatics and electromagnetism.

magnetic; → -ics.


Fr.: magnétisme   

The science of magnetic phenomena, including the fields and forces produced by magnets and, more generally, by moving electric charges.

N.L. magnetismus; → magnet + → -ism.


Fr.: magnétisation   

1) General: The process of magnetizing or the state of being magnetized.
2) Electricity: The → magnetic moment per unit volume induced by an external magnetic field; measured in → amperes per meter.

Verbal noun of → magnetize.


Fr.: magnétiser   

To make a magnet of, or impart the properties of a magnet to.

From → magnet + → -ize.


Fr.: magnétisé   

Having been made magnetic; magnetic properties imparted to.

Past participle of → magnetize.

magnetized plasma
  پلاسمای ِ مغناتیده   
pelâmâ-ye meqnâtidé

Fr.: plasma magnétisé   

A plasma containing a magnetic field which is strong enough to change the path of charged particles. It can be a → collisional plasma or → noncollisional plasma.

magnetized; → plasma.

magnetized vacuum
  خلأ ِ مغناتیده   
xala'-e meqnâtidé

Fr.: vide magnétisé   

Empty space influenced by very strong → magnetic field. Same as → birefringent vacuum.

magnetized; → vacuum.

  مغنات-، مغناتو-   
meqnât-, meqnâto-

Fr.: magnéto-, magnét-   

The prefix form of → magnet, representing magnetic or magnetism in compound words, such as → magnetogram, → magnetohydrodynamics.


magnetocentrifugal acceleration
  شتاب ِ مغنات-مرکزگریز   
šetâb-e meqnât-markazgoriz

Fr.: accelération magnetocentrifuge   

The acceleration exerted on the plasma particles according to the → magnetocentrifugal model.

magnetocentrifugal model; → acceleration.

magnetocentrifugal model
  مدل ِ مغنات-مرکزگریز   
model-e meqnât-markazgoriz

Fr.: modèle magnétocentrifuge   

A → magnetohydrodynamic model devised to account for the → bipolar jets and → outflows observed around → protostars. Basically, a → poloidal magnetic field is frozen into a rotating → accretion disk. If the angle between the magnetic field lines threading the disk and the rotation axis of the disk is larger than 30°, the plasma can be accelerated out of the accretion disk along the field lines. The field lines rotate at a constant → angular velocity, and as the gas moves outward along the field lines, it is accelerated by an increasing → centrifugal force (magnetocentrifugal acceleration). At some point, when the rotation velocity is about the same as the → Alfven velocity in the gas, the field lines get increasingly wound up by the inertia of the attached gas and a strong → toroidal magnetic field component is generated. The toroidal component is the main agent in collimating the flow into a direction along the → open magnetic field lines. The earliest version of the model was proposed by Blandford & Payne (1982, MNRAS 199, 883). It has two main versions: → X-wind and → disk wind models. See also → magnetorotational instability.

magneto-; → centrifugal; → model.

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