A small magnetic disturbance whose magnetograph resembles an indentation of a coastline. On earth, magnetic bays occur mainly in the polar regions and have duration of a few hours.



Related Terms

UNIVERSAL POLAR STEREOGRAPHIC GRID

A military grid system based on the polar stereographic map projection, applied to maps of the earth’s polar regions north of 84° N and south of 80° S.

POLAR MARITIME AIR

An air mass that originates in the polar regions and is then modified by passing over a relatively warm ocean surface. It is characterized by moderately low temperature, moderately high surface specific humidity, and a considerable degree of vertical instability. When the air is colder than the sea surface, it is further characterized by gusts and squalls, showery precipitation, variable sky, and good visibility between showers.

PRIME GRID MERIDIAN

The reference meridian of a grid. In polar regions it is usually the 180°-0° geographic meridian, used as the origin for measuring grid longitude.

MAGNETIC CIRCLE

A sphere of specified radius about the magnetic compass location to be kept free of any magnetic or electrical equipment which would interfere with the compass.

FLOAT CHAMBER

A sealed, hollow part attached to the compass card of a magnetic compass as part of the compass card assembly, to provide buoyancy to reduce the friction on the pivot bearing

ELECTROMAGNETIC WAVES

Waves of associated electric and magnetic fields characterized by variations of the fields. The electric and magnetic fields are at right angles to each other and to the direction of propagation. The waves are propagated at the speed of light and are known as radio (Hertzian) waves, infrared rays, light, ultraviolet rays, X-rays, etc., depending on their frequencies.

MAGNETIC LOUDSPEAKER

[ENG ACOUS] Loudspeaker in which acoustic waves are produced by mechanical forces resulting from magnetic reactions. Also known as magnetic speaker.

MAGNETIC FORCE

The strength of a magnetic field. Also called MAGNETIC INTENSITY.

OPTICALLY PUMPED MAGNETOMETER

A type of magnetometer that measures total magnetic field intensity by observation of the precession frequency of magnetic atoms, usually gaseous rubidium, cesium, or helium, which are magnetized by irradiation with circularly polarized light of a suitable wavelength.

CORNER REFLECTOR

A radar reflector consisting of three mutually perpendicular flat reflecting surfaces designed to return incident electro- magnetic radiation toward its source. The reflector is used to render objects such as buoys and sailboats more conspicuous to radar observations. Since maximum effectiveness is obtained when the incident beam coincides with the axis of symmetry of the reflector, clusters of reflectors are sometimes used to insure that the object will be a good reflector in all directions. Also called TRIHEDRAL REFLECTOR.

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