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The Compass

Effects of atmospheric Disturbances on the Compass


Magnetic compasses sometimes can be rendered inaccurate by a lightning strike on the vessel, or by arc welding in the close vicinity of a magnetic compass (compass should be temporarily removed while welding in the vicinity).

Lightning stikes will also affect the reliability of the GPS receiver and other on-board electronic navigation systems.

Magnetic and Ionospheric Storms

Disturbances on the sun may cause disturbances of the magnetic compass needle and interference with radio communications. At the time of an intense solar flare or eruption, a flash of ultra-violet light and a stream of charged particles are emitted from the Sun. The flash of ultra-violet light takes only 8 minutes to reach the Earth, where it produces great ionization (electrification) at abnormally low layers of the upper atmosphere.

In and near auroral zones currents of the order of a million amperes may circulate in the upper atmosphere. The magnetic field of the fluctuating currents is appreciable at the Earth's surface and may deflect a compass needle noticeably from its normal position. The effects on these so-called magnetic and ionospheric storms, which may persist with varying intensity for several days, are usually greatest in higher latitudes.

Deviations of the magnetic compass by several degrees are not uncommon in and near auroral zones.

When a great aurora is seen in abnormally low latitudes, it is invariably accompanied by a magnetic and ionospheric storm. Unlike the "radio fade-out" which occurs only on the sunlit side of Earth, the interference with radio communications which accompanies an aurora and magnetic storm may occur by day and at night.

All these effects occur most frequently and in most intense forms at the time of sunspot maximum; maxima are likely to occur in 2001-02 with a repetition time of about 11 years.

Increases in solar activity could also affect the reliability of GPS navigation and other satellite systems (supplying communication systems).

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