An Etymological Dictionary of Astronomy and Astrophysics
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A temporary, worldwide disturbance of the Earth's magnetic field by streams of charged particles from the Sun. Magnetic storms are frequently characterized by a sudden onset, in which the magnetic field undergoes marked changes in the course of an hour or less, followed by a very gradual return to normalcy, which may take several days.

→ magnetic; → storm.

A property of material defined by the ratio of the → magnetization to the → magnetic intensity. In other words, the magnetization per unit magnetic intensity.

→ magnetic; → susceptibility.

A continuous, flexible ribbon impregnated or coated with magnetic-sensitive material on which information (sound, images, data, etc.) may be recorded.

→ magnetic; → tape.

In → magnetohydrodynamic (MHD) treatment of → plasmas, that component of the → Lorentz force which is directed toward the centre of curvature of the → magnetic field lines and thus acts to straighten out the field lines. The Lorentz force can be decomposed into two components orthogonal to the magnetic field: j× B = (B . ∇) B / μ₀ - ∇ (B² / 2μ₀), where j is the → current density, μ₀ is the → magnetic permeability of free space, and B is the → magnetic flux density. The left side term is the Lorentz force, the first term on the right side is the magnetic tension and the second term the → magnetic pressure.

→ magnetic; → tension.

A vector field A defined so that the → magnetic field  B is given by its → curl: B = ∇ x A.

→ magnetic; → vector; → potential.

Radiation emitted by a rotating magnet.

→ magnetic; → dipole; → radiation.

The study of magnetic phenomena, comprising magnetostatics and electromagnetism.

→ magnetic; → -ics.

The science of magnetic phenomena, including the fields and forces produced by magnets and, more generally, by moving electric charges.

N.L. magnetismus; → magnet + → -ism.

An international collaboration devoted to the study of the origin and physics of → magnetic fields in → massive stars. The project uses several observatories and a large number of telescopes equipped with → spectropolarimetric and → asteroseismologic instruments, including → HARPS, → HARPSpol, and → ESPaDOnS (Wade et al., 2016, MNRAS 456, 2).

→ magnetism; → massive; → star.

1) General: The process of magnetizing or the state of being magnetized.
2) Electricity: The → magnetic moment per unit volume induced by an external magnetic field; measured in → amperes per meter.

Verbal noun of → magnetize.

To make a magnet of, or impart the properties of a magnet to.

From → magnet + → -ize.

Having been made magnetic; magnetic properties imparted to.

Past participle of → magnetize.

A plasma containing a magnetic field which is strong enough to change the path of charged particles. It can be a → collisional plasma or → noncollisional plasma.

→ magnetized; → plasma.

Empty space influenced by very strong → magnetic field. Same as → birefringent vacuum.

→ magnetized; → vacuum.

The prefix form of → magnet, representing magnetic or magnetism in compound words, such as → magnetogram, → magnetohydrodynamics.

→ magnet.

Combined study of the large-scale → magnetic field (→ magnetometry) and → stellar pulsations (→ asteroseismology). Magneto-asteroseismology provides strong complementary diagnostics suitable for detailed stellar modeling and permits the determination of the → internal structure and conditions within → magnetic massive  → pulsators, for example the effect of magnetism on → mixing processes. More specifically, asteroseismology yields information on the → density, → composition, and → chemical mixing in multiple internal layers (depending on the number of studied frequencies). Additionally, when rotationally split pulsation modes are observed, the internal rotation profile can be retrieved. From magnetometry surface properties are determined, related to the → chemical composition, including → starspots, and the magnetic field, such as its geometry, obliquity, and strength. Magnetic studies also provide constraints about the → stellar wind geometry and the → circumstellar environment. Moreover, the stellar → rotation period period and the → angle of inclination toward the observer are also retrieved (Buysschaert et al., 2017, astro-ph/1709.02619).

→ magneto-; → asteroseismology.

The acceleration exerted on the plasma particles according to the → magnetocentrifugal model.

→ magnetocentrifugal model; → acceleration.

A → magnetohydrodynamic model devised to account for the → bipolar jets and → outflows observed around → protostars. Basically, a → poloidal magnetic field is frozen into a rotating → accretion disk. If the angle between the magnetic field lines threading the disk and the rotation axis of the disk is larger than 30°, the plasma can be accelerated out of the accretion disk along the field lines. The field lines rotate at a constant → angular velocity, and as the gas moves outward along the field lines, it is accelerated by an increasing → centrifugal force (magnetocentrifugal acceleration). At some point, when the rotation velocity is about the same as the → Alfven velocity in the gas, the field lines get increasingly wound up by the inertia of the attached gas and a strong → toroidal magnetic field component is generated. The toroidal component is the main agent in collimating the flow into a direction along the → open magnetic field lines. The earliest version of the model was proposed by Blandford & Payne (1982, MNRAS 199, 883). It has two main versions: → X-wind and → disk wind models. See also → magnetorotational instability.

→ magneto-; → centrifugal; → model.

A graphic representation of solar magnetic field strengths and polarity.

From → magneto- + → -gram.

Of or relating to → magnetohydrodynamics.

→ magneto- + → hydrodynamic.