Periodic and Non-Periodic Components in Geomagnetic Secular Variation
Yanagihara, K.
Abstract
Periodic component of geomagnetic secular variation is found when the non-periodic change is reduced from observed values. Its period and amplitude are often determined wrongly by careless estimate of the non-periodic component，such as simple approximation by a power function of time. The method of least squares should be applied to a sum of non-periodic and periodic terms. This is discussed in this paper. And then the analysis is made for 10 observatories’ mean secular variation. Its period is about 60 years with the amplitude of 15ー16γ/yr in H or D.
