gir-oft-e tâbeši, gir-andâzi-ye ~
Fr.: capture radiative
Capture of a free electron by an ion with the subsequent emission of photons; also called → radiative recombination.
Fr.: collision radiative
A collision between charged particles in which part of the kinetic energy is converted into electromagnetic radiation.
Fr.: refroidissement radiatif
The process by which temperature decreases due to an excess of emitted radiation over absorbed radiation.
Fr.: désexcitation radiative
The process when the energy difference between the excited and non excited states of an atom is taken away by radiation.
Fr.: diffusion radiative
A process of → radiative transfer in which photons are repeatedly absorbed and re-emitted by matter particles.
Fr.: envelope radiative
A → radiative zone occupying the outer parts of a star.
Fr.: équilibre radiatif
The balance between radiative emission and radiative absorption in a specified system.
Fr.: rétroaction radiative
The radiative energy put back to the environment through an astrophysical process. For example, in the process of → star formation → accretion disks form around → protostars. The material in the disk spirals inward and on to the protostar, provided that there is an efficient mechanism to redistribute → angular momentum outward in the disk. During this process → gravitational energy is transformed into radiation due to → viscous dissipation in the disk and at the → accretion shock around the protostar. This radiation heats the region around the protostar and may → suppress subsequent → fragmentation and further star formation. Thus, radiative feedback plays a critical role in regulating the stellar → initial mass function.
Fr.: flux radiatif
The radiative energy per unit time and unit area.
Fr.: chauffage radiatif
The process by which temperature increases due to an excess of absorbed radiation over emitted radiation.
Fr.: lévitation radiative
A physical process occurring in → stellar atmospheres whereby → radiation pressure selectively pushes certain → chemical elements outward, leading to an atmospheric overabundance of such elements. See also → gravitational settling.
Fr.: phase radiative
Fr.: processus radiatif
An process in which an excited state loses its absorbed energy by emission of radiation. → non-radiative process.
Fr.: recombinaison radiative
The process by which an ionized atom binds a free electron in a → plasma to produce a new atomic state with the subsequent radiation of photons.
toš-e tâbeši, šok-e ~
Fr.: choc radiatif
A → shock wave in which the → time-scale for → cooling is much shorter than the appropriate → dynamical or → evolutionary time-scale of the system that drives the shock. Radiative shock waves are believed to play a key role in a variety of different astrophysical environments, including → magnetic cataclysmic variables, → jets from → young stellar objects, → accretion in → T Tauri stars, → colliding stellar winds, and → supernova remnants.
tarâvâž-e tâbeš, ~ tâbeši
Fr.: transfer radiatif, ~ de rayonnement
radiative transfer equation
hamugeš-e tarâvaž-e tâbeš
Fr.: équation de transfer radiatif, ~ ~ de rayonnement
The equation that describes the → radiative transfer. It states that the → specific intensity of radiation Iσ during its propagation in a medium is subject to losses due to → extinction and to → gains due to → emission: dIσ/dx = - μσ . Iσ + ρ . jσ, where x is the coordinate along the → optical path, μσ is the → extinction coefficient, ρ is the mass → density, and jσ is the → emission coefficient per unit mass.
Fr.: transition radiative
A transition between two states of an atomic or molecular entity, the energy difference being emitted or absorbed as photons.
Fr.: zone radiative
The region of a star in which the energy generated by → nuclear fusion in the core is transferred outward by → electromagnetic radiation and not by → convection. Such zones occur in the interior of low-mass stars, like the Sun, and the envelopes of → massive star. The radiative zone of the Sun starts at the edge of the core of the Sun, about 0.2 solar radii, and extends up to about 0.7 radii, just below the → convective zone.
radiatively driven wind
Fr.: vent radiatif
Same as → radiation-driven wind