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.

ELECTRON-BEAM CHANNELING

The technique of transporting high-energy, high-current electron beams from an accelerator to a target through a region of high-pressure gas by creating a path through the gas where the gas density may be temporarily reduced; the gas may be ionized; or a current may flow whose magnetic field focuses the electron beam on the target.

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.

MAGNETIC FORCE

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

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.

HEELING MAGNET

A permanent magnet placed vertically in a tube under the center of a marine magnetic compass, to correct for heeling error.

SPIRIT COMPASS

A magnetic compass of which the bowl mounting the compass card is filled with a solution of alcohol and water.

ISODYNAMIC LINE

A line connecting points of equal magnetic intensity, either the total or any component

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