An Etymological Dictionary of Astronomy and Astrophysics
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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.

In the → solar dynamo model, a magnetic field that points from east to west or vice-versa.

→ azimuthal; → magnetic; → field.

A → magnetic field whose lines of force (→ line of force) run around the perimeter of the magnet.

→ circular; → magnetic; → field.

A → magnetic field produced by a system possessing a net magnetic → dipole moment.

→ dipolar; → magnetic; → field.

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.

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.

→ force; → free; → magnetic; → field.

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.

→ fossil;→ magnetic; → field;

A → magnetic field line in a → fluid when the motion of the fluid carries the magnetic field along with it.

Frozen, p.p. of → freeze; → magnetic; → line.

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.

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.

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.

1) A → magnetic field whose lines of force (→ line of force) run parallel to the long axis of the → magnet. Longitudinal magnetization 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.
2) In → stellar magnetic field observations, the magnetic field along the → line of sight.

→ longitudinal; → magnetic; → field.

A field of force that is generated by electric currents, or, equivalently, a region in which magnetic forces can be observed.

→ magnetic; → field.

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.

Same as → magnetic intensity.

→ magnetic; → field; → intensity.

In the → solar dynamo model, a magnetic field that points from the north to south or south to north.

→ meridional; → magnetic; → field.

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.

→ open; → magnetic; → field; → line.

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.
2) In a → tokamak, the magnetic field produced by a current flowing in the → plasma vertically to the toroid plane. → toroidal magnetic field.

→ pole; → -oid; → magnetic field.

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.

→ solar; → magnetic; → field.

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).

→ stellar; → magnetic; → field.