tarâvâyi-ye meqnâtisi (#)
Fr.: perméabilité magnétique
The ratio of the → magnetic induction, B, in the substance to the external magnetic field, H, causing the → induction: μ = B/H. It is measured in henry/meter and is known as absolute permeability. The relative permeability is equal to the ratio of absolute permeability to the permeability of the free space. Thus μr = μ/μ0, where μ0, the permeability of free space has the value 4π x 10-7 henry/meter.
qotb-e meqnâtisi (#)
Fr.: pôle magnétique
1) The region of a magnet toward which the lines of magnetic force
converge (south pole) or from which the lines of force diverge
magnetic Prandtl number
adad-e Prandtl-e meqnâtisi
Fr.: nombre de Prandtl magnétique
A → dimensionless quantity used in → magnetohydrodynamics to describe the relative balance of → kinematic viscosity to → magnetic diffusion. It is described by: Pr = σμ0ν = ν/η, where σ is the → conductivity of the fluid, μ0 is the → magnetic permeability of the fluid, ν is the kinematic viscosity of the fluid, and η is the → magnetic diffusivity.
fešâr-e meqnâtisi (#)
Fr.: pression magnétique
The pressure exerted by a magnetic field on the material that contains the field.
magnetic quantum number
adad-e kuântomi-ye meqnâtisi (#)
Fr.: nombre quantique magnétique
In atomic physics, a quantum number that denotes the energy levels available within a subshell. Designated by the letter m, it is one of a set of quantum numbers which describe the unique quantum state of an electron.
Fr.: reconnexion magnétique
In a → plasma, a change of → magnetic connectivity of plasma elements due to the presence of a localized → diffusion region. It allows charged particles to move from one → magnetic field line to another. Magnetic reconnection is an important process transforming magnetic energy into heat or/and kinetic energy. Magnetic reconnection events occur in the Earth's → magnetosphere. The process plays an important role in explosive phenomena in the Sun, such as → coronal mass ejections and → solar flares which heat the → solar corona.
Fr.: relaxation magnétique
The process by which a magnetic system relaxes to its minimum energy state over time.
bâzâvâyi-ye meqnâtisi (#)
Fr.: résonance magnétique
A phenomenon exhibited by certain atoms whereby they absorb energy at specific (resonant) frequencies when subjected to alternating magnetic fields.
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. See also → geomagnetic excursion.
magnetic Reynolds number
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.
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 south pole
qotab-e daštar-e meqnâtisi
Fr.: pôle sud magnétique
Fr.: dédoublement magnétique
A process whereby the (internal) → magnetic field of a star modifies the → pulsations by lifting some of its degeneracy. Instead of just one pulsation frequency, a multiplet of frequencies is then observed. This effect was proposed as a possible explanation for the observed frequency pattern of → Beta Cephei. In practice, the magnetic splitting is difficult to observe, because of the very small expected frequency difference between the peaks. However, when unaccounted for, it may lead to a wrong mode identification. The current best candidate to detect magnetic splitting is → HD 43317, since this star displays two close frequency patterns (Buysschaert et al., 2017, astro-ph/1709.02619).
setâre-ye meqnâtisi (#)
Fr.: étoile magnétique
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.
Fr.: susceptibilité magnétique
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 vector potential
tavand-e bordâri-ye meqnâtisi
Fr.: vecteur potentiel magnétique
tâbeš-e doqotbe-ye meqnâtisi (#)
Fr.: rayonnement du dipôle magnétique
Radiation emitted by a rotating magnet.
The study of magnetic phenomena, comprising magnetostatics and electromagnetism.