aligned magnetic field
meydân-e meqnâtisi-ye âxatidé
Fr.: champ magnétique aligné
A magnetic field whose lines of force are oriented along a particular direction or by a particular manner (axially, vertically; randomly, properly, etc.)
→ aligned; → magnetic field.
azimuthal magnetic field
meydân-e meqnâtisi-ye sugâni
Fr.: champ magnétiquue azimutal
In the → solar dynamo model, a magnetic field that points from east to west or vice-versa.
circular magnetic field
meydân-e meqnâtisi-ye dâyere-yi
Fr.: champ magnétique circulaire
A → magnetic field whose lines of force (→ line of force) run around the perimeter of the magnet.
dipolar magnetic field
meydân-e meqnâtisi-ye dipoli, ~ ~ diqotbi
Fr.: champ magnétique dipolaire
A → magnetic field produced by a system possessing a net magnetic → dipole moment.
Fr.: champ électromagnétique
A region of space consisting of coupled electric and magnetic lines of force at each point, generated by time-varying currents and accelerated charges.
→ electromagnetic; → field.
force-free magnetic field
Fr.: champ magnétique sans force
The condition in a plasma when the → Lorentz force is zero, that is when the electric current flows along the magnetic field. Force-free magnetic fields are encountered in astrophysical plasmas with negligible gas pressure. The solar corona is the best available example of such fields in action in a plasma.
fossil magnetic field
meydân-e meqnâtisi-ye sangvâré, ~ ~ sangvâre-yi
Fr.: champ magnétique fossile
In a physical system, the → magnetic field belonging to an earlier magnetic process or event. A fossil magnetic field may be a vanished one or exist in relic forms. As an example, the solar magnetic field, which was present during the formation of the Sun, has disappeared over the last 4.6 billions years.
frozen magnetic field line
xatt-e meydân-e meqnâtisi-ye yax basté, ~ ~ ~ rocidé
Fr.: ligne de champ magnétique gelée
A → magnetic field line in a → fluid when the motion of the fluid carries the magnetic field along with it.
meydân-e zamin-meqnâtisi, ~ zamin-meqnâti
Fr.: champ géomagnétique
The magnetic field that is generated within the Earth and extends out around the Earth. The intensity of the magnetic field at the Earth's surface is about 0.32 → gauss at the equator and 0.62 gauss at the north pole.
→ geomagnetic; → field.
interplanetary magnetic field
meydân-e meqnâtisi-ye andarsayyârei
Fr.: champ magnétique interstellaire
The magnetic field that is carried along with the solar wind and fills the solar system space. It is wound into a spiral structure by the rotation of the Sun. At the Earth's distance from the Sun, it has a strength of about 5 x 10-5 gauss.
→ interplanetary; → magnetic; → field.
interstellar magnetic field
meydân-e meqnâtisi-ye andaraxtari
Fr.: champ magnétique interstellaire
A large-scale, weak magnetic field, with an estimated strength of about 1 to 5 microgauss, that pervades the disk of the Milky Way Galaxy and controls the alignment of interstellar dust grains.
→ interstellar; → magnetic; → field.
longitudinal magnetic field
meydân-e meqnâtisi-ye derežnâyi
Fr.: champ magnétique longitudinal
1) A → magnetic field whose lines of force
(→ line of force)
run parallel to the long axis of the → magnet.
of a component can be accomplished using the longitudinal field set
up by a → coil or
→ solenoid. It can also be accomplished using
permanent magnets or electromagnets.
→ longitudinal; → magnetic; → field.
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 line
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 strength
zur-e meydân-e meqnâtisi
Fr.: intensité du champs magnétique
Same as → magnetic intensity.
meridional magnetic field
meydân-e meqnâtisi-ye nimruzâni
Fr.: champ magnétiquue méridien
In the → solar dynamo model, a magnetic field that points from the north to south or south to north.
→ meridional; → magnetic; → field.
open magnetic field line
xatt-e bâz-e meydân-e meqnâtisi-ye
Fr.: ligne ouverte de champ magnétique
In the context of solar physics, a → magnetic field line when it crosses the solar surface only once, i.e., when it goes from surface to infinity. This is the case at a sufficiently large scale in → coronal holes. This is mostly not the case in → active regions.
poloidal magnetic field
meydân-e meqnâtisi-ye qotbivâr
Fr.: champ magnétique poloÃ¯dal
1) In → protoplanetary disk models, the magnetic field
whose large-scale lines of force depart away from the → accretion disk,
in the direction of the rotation axis.
→ pole; → -oid; → magnetic field.
solar magnetic field
meydân-e meqnâtisi-ye xoršid (#)
Fr.: champ magnétique solaire
The Sun's magnetic field which is probably created by the → differential rotation of the Sun together with the movement of charged particles in the → convective zone. Understanding how the solar magnetic field comes about is the fundamental problem of Solar Physics. The solar magnetic field is responsible for all solar magnetic phenomena, such as → sunspots, → solar flares, → coronal mass ejections, and the → solar wind. The solar magnetic fields are observed from the → Zeeman broadening of spectral lines, → polarization effects on radio emission, and from the channeling of charged particles into visible → coronal streamers. The strength of Sun's average magnetic field is 1 → gauss (twice the average field on the surface of Earth, around 0.5 gauss), and can be as strong as 4,000 Gauss in the neighborhood of a large sunspot.
stellar magnetic field
meydân-e meqnâtisi-ye setâre-yi
Fr.: champ magnétique stellaire
The → magnetic field associated with a star. Magnetic fields are common among stars of solar and lower masses. So far definitive detections of fields in stars with masses ~1.5 Msun have, for the most part, been made for objects having anomalous chemical abundances (e.g., the → chemically peculiar A and B stars). Recently, however, observations of cyclic variability in the properties of → stellar winds from luminous → OB stars have been interpreted as evidence for the presence of large-scale magnetic fields in the surface layers and atmospheres of these objects (→ magnetic massive star). These inferences have been bolstered by the unambiguous measurement of a weak (~ 360 G) field in the chemically normal B1 IIIe star → Beta Cephei. These results suggest that magnetic fields of moderate strength might be more prevalent among → hot stars than had previously been thought. At the present time, the origin of magnetism in massive stars is not well understood. If the magnetic field of a hot star is produced by → dynamo effect in the → convective core, then a mechanism for transporting the field to the stellar surface must be identified. The finite electrical conductivity of the envelope leads to the outward diffusion of any fields contained therein, but only over an extended period of time. Estimates indicate that for stars more massive than a few solar masses, the resistive diffusion time across the radiative interior exceeds the → main sequence lifetime. Another possibility is that dynamo fields are advected from the core to the surface by rotation-induced → meridional circulation (MacGregor & Cassinelli, 2002, astro-ph/0212224).