# MAGNETIC TEMPORAL VARIATION

Any change in the earth’s magnetic field which is a function of time.

## Related Terms

### ARMATURE DEMAGNETIZATION

The reduction in the effective magnetic lines of force, produced by the armature current.

### ANALYTICAL FERROGRAPHY

The magnetic precipitation and subsequent analysis of wear debris from a fluid sample .This approach involves passing a volume of fluid over a chemically treated microscope slide which is supported over a magnetic field. Permanent magnets are arranged in such a way as to create a varying field strength over the length of the substrate. This varying strength causes wear debris to precipitate in a distribution with respect to size and mass over the Ferrogram. Once rinsed and fixed to the substrate, this debris deposit serves as an excellent media for optical analysis of the composite wear particulates.

### AIR GAP

The space between magnetic poles, or between the rotating and stationary assemblies in a motor or generator.

### HALVING

The process of adjusting magnetic compass correctors so as to remove half of the deviation on the opposite cardinal or adjacent intercardinal headings to those on which adjustment was originally made when all deviation was removed. This is done to equalize the error on opposite headings.

### HEELING MAGNET

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

### GRID MAGNETIC ANGLE

Angular difference in direction between grid north and magnetic north. It is measured east or west from grid north. Grid magnetic angle is sometimes called GRID VARIATION or GRIVATION.

A dip needle with a sliding weight that can be moved along one of its arms to balance magnetic force, used to determine the correct position of a heeling magnet.

### HEELING ERROR

The change in the deviation of a magnetic compass when a craft heels, due to the change i

### MAGNETIC BEARING

A type of bearing in which the force that separates the relatively moving surfaces is produced be a magnetic field.

### MAGNETIC BEARING

A type of bearing in which the force that separates the relatively moving surfaces is produced be a magnetic field.

### Related questions

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