Fr.: milieu non dispersif
A medium in which the → phase velocity is independent of frequency.
hendese-ye nâ-oqlidosi (#)
Fr.: géométrie non-euclidienne
Any of several geometries which do not follow the postulates and results of Euclidean geometry. For example, in a non-Euclidean geometry through a point several lines can be drawn parallel to another line. Or, the sum of the interior angles of a triangle differs from 180 degrees. According to Einstein's general relativity theory, gravity distorts space into a non-Euclidean geometry.
non-hierarchical multiple system
râžmân-e bastâyi-ye nâpâygâni
Fr.: système multiple non hiérarchique
cârcub-e nâlaxtinâk, ~ nâlaxtimand
Fr.: référentiel non inertiel, ~ non galiléen
Any frame of reference in which the law of inertia does not apply, such as in accelerating and rotating frames. For example, the Earth is a non-inertial frame because it is rotating about its axis. But the rotation is so slow that the associated acceleration is negligible compared to other accelerations commonly encountered in everyday life. However, the non-inertial nature of the Earth appears in, e.g., the → Coriolis effect. → inertial reference frame.
Fr.: non ionisé
Not ionized, → neutral.
non-local thermodynamic equilibrium (NLTE)
tarâzmandi-ye garmâtavânik-e nâmahali
Fr.: hors équilibre thermodynamique local
A physical condition in which the assumption of the → local thermodynamic equilibrium does not hold.
Fr.: matière non lumineuse
Not ordinary matter. Same as → dark matter.
Fr.: pulsation non-radiale
A type of stellar pulsation in which waves run in different directions on and beneath the surface of a star.
Fr.: processus non radiatif
An process in which an excited state returns to the ground state without emitting radiation. → radiative process.
Fr.: électron non-relativiste
An electron that does not experience relativistic effects since its velocity is very small compared to that of light.
Fr.: mécanique non-relativiste
Mechanics in which the masses under consideration move at speeds much slower than the speed of light.
Fr.: non thermique
The nature of a → non-thermal radiation.
gosil- nâgarmâyi (#)
Fr.: émission non thermique
non-thermal filament (NTF)
Fr.: filament non thermique
Any of many long and slender structures visible in → radio continuum images of the inner hundred parsecs of the → Galactic Center. NTFs are typically tens of parsecs long and only a fraction of parsec wide. They may occur in isolation or in bundles, such as those comprising the linear portion of the prominent → radio Arc. Their → non-thermal spectrum and strong → linear polarization indicate → synchrotron radiation. The magnetic fields in the NTFs have been estimated from various means. Early estimates centered on the radio Arc, and focused on a comparison between the → magnetic pressure and the estimated → ram pressure from nearby → molecular cloud interactions, indicated magnetic field strengths as high as 1 mG (Morris and Yusef-Zadeh 1985). More recent observations, however, have pointed to significantly weaker magnetic fields among the population of NTFs. Synchrotron models of the radio spectrum imply equipartition magnetic fields between 50-200 μG. Theoretically, it has been challenging to understand the nature of these filaments that resemble extragalactic → radio jets but are not accompanied with any obvious source of acceleration of charged particles to high energy → relativistic energies. Although a number of detailed models have been considered, there is no consensus as to the origin of the NTFs. These models suggest that molecular and ionized gas clouds, mass-losing stars, → Galactic winds, magnetic activity of the → supermassive black hole at the Galactic center, and → lepton production due to → dark matter annihilation play a role in the processes that lead to the production of the NTFs (Linden et al. 2011, ApJ 741,95, and references therein). In most models, the magnetic field is strong and its global geometry in the central region of the Galaxy is considered to be → poloidal and static. However, some recent models have argued that the magnetic field is local and dynamic.
tâbeš-e nâgarmâyi (#)
Fr.: rayonnement non thermique
The electromagnetic radiation whose characteristics do not depend on the temperature of the emitting source. In contrast to → thermal radiation, it has a different spectrum from that of → blackbody radiation. The three common types of non-thermal radiation in astronomy are: → synchrotron radiation, → bremsstrahlung radiation, and → maser → stimulated emission.
Fr.: spectre non thermique
A radio emission with a negative → spectral index. In this type of emission the intensity of the emitted radiation increases with wavelength.
Fr.: non zéro, non nul
Not equal to zero.
Fr.: polynôme non nul
Fr.: diffusion incohérente
The absorption of a photon and its re-emission at a different frequency (in the observer's frame of reference) by scattering atoms.