# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 magnetic convection   همبز ِ مغناتیسی   hambaz-e meqnâtisiFr.: convection magnétique   Thermal → convection modified by the presence of magnetic fields.→ magnetic; → convection. magnetic declination   واکیلش ِ مغناتیسی   vâkileš-e meqnâtisiFr.: déclinaison magnétique   In terrestrial magnetism, the difference between → true north (the axis around which the earth rotates) and magnetic north (the direction the needle of a compass will point,→ magnetic pole).→ magnetic; → declination. magnetic diffusion   پخش ِ مغناتیسی   paxš-e meqnâtisiFr.: diffusion magnétique   The process whereby the magnetic field tends to diffuse across the plasma and to smooth out any local inhomogeneities under the influence of a finite resistance in the plasma. For a stationary plasma the → induction equation becomes a pure → diffusion equation: ∂B/∂t = Dm∇2B, where Dm = (μ0σ0)-1 is the → magnetic diffusivity.→ magnetic; → diffusion. magnetic diffusivity   پخشندگی ِ مغناتیسی   paxšandegi-ye meqnâtisiFr.: diffusivité magnétique   The → diffusion coefficient for a magnetic field. It is expressed as: η = 1/(μ0σ), where μ0 is the → magnetic permeability and σ the → conductivity.→ magnetic; → diffusivity. magnetic dip   نشیب ِ مغناتیسی   našib-e meqnâtisiFr.: inclinaison magnétique   In terrestrial magnetism, the angle that a → magnetic needle makes with the horizontal plane at any specific location. The angle of magnetic dip at the → magnetic poles of Earth is 90°. Also called → inclination and → dip.→ magnetic; → dip. magnetic dipole   دوقطبه‌ی ِ مغناتیسی   doqotbe-ye maqnâtisiFr.: dipole magnétique   A system that generates a → magnetic field in which the field is considered to result from two opposite poles, as in the north and south poles of a magnet, much as an → electric field originates from a positive and a negative charge in an → electric dipole. A loop carrying an electric current also acts as a magnetic dipole. Magnetic dipoles experience a torque in the presence of magnetic fields. → dipole moment; → magnetic moment.→ magnetic; → dipole. magnetic dipole moment   گشتاور ِ دوقطبه‌ی ِ مغناتیسی   gaštâvar-e doqotbe-ye meqnâtisiFr.: moment dipolaire magnétique   Same as → magnetic moment.→ magnetic; → dipole; → moment. magnetic domain   دمن ِ مغناتیسی   daman-e meqnâtisiFr.: domaine magnétique   Any of several microscopic areas in a → ferromagnetic material that possesses a net → magnetic field, because electron spins are aligned in the same direction. In the absence of an external magnetic field, the directions of the magnetization vectors of the separate domains do not coincide and the resultant magnetization of the whole body may be zero.→ magnetic; → domain. magnetic energy   کاروژ ِ مغناتیسی   kâruž-e meqnâtisiFr.: énergie magnétique   The energy stored in a magnetic field. It is the → work that must be done to establish a magnetic field in terms of the → magnetic induction. Magnetic energy varies as the square of the magnetic induction. It can be expressed in several other ways, for example in terms of the current and of the magnetic flux, or in terms of the current density and vector potential.→ magnetic; → energy. magnetic field   میدان ِ مغناتیسی   meydân-e meqnâtisi (#)Fr.: champ magnétique   A field of force that is generated by electric currents, or, equivalently, a region in which magnetic forces can be observed.→ magnetic; → field. magnetic field line   خط ِ میدان ِ مغناتیسی   xatt-e meydân-e meqnâtisi (#)Fr.: ligne de champ magnétique   An imaginary line used for representing the strength and direction of a magnetic field. Charged particles move freely along magnetic field lines, but are inhibited by the magnetic force from moving across field lines.→ magnetic; → field; → line. magnetic field strength   زور ِ میدان ِ مغناتیسی   zur-e meydân-e meqnâtisiFr.: intensité du champs magnétique   Same as → magnetic intensity.→ magnetic; → field; → intensity. magnetic flux   شار ِ مغناتیسی   šâr-e meqnâtisi (#)Fr.: flux magnétique   A measure of the quantity of magnetism or magnetic field. It is the number of lines of force passing normally through a given area. Magnetic flux is a scalar quantity defined as the surface integral of the → magnetic flux density. It is usually denoted by the Greek letter Φ and its SI unit is the → weber.→ magnetic; → flux. magnetic flux density   چگالی ِ شار ِ مغناتیسی   cagâli-ye šâr-e meqnâtisi (#)Fr.: densité du flux magnétique   A vector quantity measuring the strength and direction of the magnetic field. It is the → magnetic flux per unit area of a magnetic field at right angles to the magnetic force. Magnetic flux density is expressed in → teslas. Also called → magnetic induction.→ magnetic; → flux; → density. magnetic helicity   پیچاری ِ مغناتیسی   picâri-ye meqnâtisiFr.: hélicité magnétique   A quantity that measures the extent to which the magnetic field lines wrap and coil around each other. It is closely related to field line topology. Magnetic helicity is defined by: HM = ∫ A . B dV, where A is the vector potential of the magnetic field and the integration is over a volume V. → helicity; → kinetic helicity→ magnetic; → helicity. magnetic inclination   درکیل ِ مغناتیسی   darkil-e meqnâtisiFr.: inclinaison magnétique   Same as → magnetic dip or → dip.→ magnetic; → inclination. magnetic induction   درهازش ِ مغناتیسی   darhâzeš-e meqnâtisiFr.: induction magnétique   1) Same as → magnetic flux density. 2) The production of a magnetic field in a piece of un-magnetized iron or other → ferromagnetic substance when a magnet is brought near it. The magnet causes the individual particles of iron, which act like tiny magnets, to line up so that the sample as a whole becomes magnetized.→ magnetic; → induction. magnetic intensity   درتنویی ِ مغناتیسی   dartanuyi-e meqnâtisiFr.: intensité magnétique   Strength of a magnetic field at a point, denoted H. The force which could be exerted on unit north magnetic pole situated at that point. Measured in oersteds. Same as → magnetic field strength.→ magnetic; → intensity. magnetic massive star   ستاره‌ی ِ پرجرم ِ مغناتیسی   setâre-ye porjerm-e meqnâtisiFr.: étoile massive magnétique   A → stellar magnetic field associated with a → massive star. Magnetic fields are detected only for seven to ten percent of all studied massive → OB stars, and the magnetic field occurrence does not depend on the → spectral type. Because these magnetic fields seem to be stable over long time-scales and their strength does not seem to correlate with known stellar properties, it is assumed that they are of fossil origin (→ fossil magnetic field) and are frozen into the → radiative envelope of the stars. The fields are those of the birth → molecular clouds, partly trapped inside the → pre-main sequence star during the cloud → collapse phase, possibly further enhanced by a → dynamo effect in the early fully convective stellar phase. Typically, the polar field strength ranges from about a hundred → Gauss up to several kiloGauss. However, some weaker fields, below 100 G, have recently been detected. The stellar magnetic field influences many different regions of the star with various effects. In the deep interior of the star, the field influences the internal → mixing of the star and this affects the size of the → convective overshooting region, changing the lifetime of the star by decreasing the amount of fuel for nuclear burning. Magnetic stars can also confine their → stellar winds, due to their strong magnetic fields, into a → magnetosphere, which slows down the → rotational velocity of the star. This → magnetic braking is an efficient mechanism for → angular momentum transport. At the stellar surface, the magnetic fields can create and sustain areas of chemical over- or under-abundances and/or large temperature differences, which are called spots (Buysschaert et al., 2016, astro-ph/1709.02619).→ magnetic; → massive; → star. magnetic meridian   نیمروزان ِ مغناتیسی   nimruzân-e meqnâtisiFr.: méridien magnétique   A meridian passing through the Earth's → magnetic poles.→ magnetic; → meridian.