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Magnetic Measurements >
Secular Variations
Secular Variations of the Earth Magnetic Field
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The slow variations of the geomagnetic field elements are referred to as the
secular variations; their value is about tens gammas a year.
Secular variations of elements are driven by the changing pattern of motion in the Earth core,
and are caused by the same reasons as the Earth magnetic field itself.
Change the annual mean values of either element within a year is called secular way.
Annual mean values of the Earth's magnetic field elements could be obtained only in observatories,
but their number is limited, that’s why it’s recommended to use daily means data from
observations taken at another Earth’s surface points through certain time gaps, but no more
than through 3-5 years. In this case secular way is determined as a difference
between two such measurements divided by the period of time in years. Sites, where repeated measurements
of the Earth’s magnetic elements are held, are called
secular variation points.
Secular variation isn’t constant in time and changes from one epoch to another.
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