An Etymological Dictionary of Astronomy and Astrophysics
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The electric or magnetic field that is derived from the → retarded potentials.

Retarded, adj. of → retard; → field.

A → field whose value at every point of space is independent of → direction and → position. Examples include → temperature distribution throughout space and → pressure distribution in a → fluid. Similarly, a → potential field, such as the Newtonian → gravitational field or the electric potential in → electrostatics are scalar fields. In quantum field theory, a scalar field is associated with → spin zero particles, such as → mesons or → bosons. Therefore, the → Higgs boson is associated with a scalar field. The → derivative of a scalar field results in a → vector field is called the → gradient. In contrast to a vector field, a scalar field is → invariant under the → rotation of the → coordinate system. The → inflation in the → early Universe is supposed to be driven by a scalar field, called the → inflaton field.

→ scalar; → 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 distribution of → sound energy in a defined space.

→ sound; → 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.

The area over which the → meteorite fragments from a particular → fall are dispersed.

Strewn, p.p. of strew, from M.E. strewen, O.E. strewian; cf. O.S. stroian, O.N. stra, Dan. strø, Swed. strö, M.Du. strowen, Du. strooien, O.H.G. strouwen, Ger. streuen, Goth. straujan "to sprinkle, strew;" PIE base *stere- "to spread, extend, stretch out;" from which Pers. gostar-, gostardan "to stretch, expand;" Av. star- "to spead out;" → field.

Meydân, → field; paxš "scattered," → diffuse.

A field of space and time each point of which has multiple directionality, and is describable by a tensor function.

→ tensor; → field.

A magnetic field which is generated in a → plasma inside a → toroid, as in a → tokamak, by the electric current which spirals around the toroid. Toroidal field has no radial component. → poloidal magnetic field.

→ toroid; → magnetic field.

A field that at a given instant has the same value at all points within a specified region of interest.

→ uniform; field.

A → magnetic field whose direction does not change and whose strength is constant at every point.

→ uniform; → magnetic; → field.

A vector each of whose → components is a → scalar field. For example, the → gradient of the scalar field F, expressed by: ∇F = (∂F/∂x)i + (∂F/∂y)j + (∂F/∂z)k.

→ vector; → field.

A telescope → field of view which covers a relatively large → angular area on the sky.

→ wide; → field.

A → NASA infrared astronomical → space telescope launched in December 2009 to carry out an → all-sky survey from 3 to 22 → microns. With its 40-cm → telescope telescope and → infrared cameras, WISE aimed at a wide variety of studies ranging from the evolution of → protoplanetary disks to the history of → star formation in normal galaxies. In early October 2010, after completing its prime science mission, the spacecraft ran out of → coolant that keeps its instrumentation cold. However, two of its four infrared cameras remained operational. Hence, NASA extended the NEOWISE portion of the WISE mission by four months, with the primary purpose of hunting for more → asteroids and → comets, and to finish one complete scan of the main → asteroid belt. In August 2013, the WISE telescope's mission was extended for more three years to search for asteroids that could collide with Earth.

→ wide field; → infrared; → survey; → explorer.