Fluctuations in geomagnetic secular variation rate according to data from the global network of magnetic observatories

Abstract

Abstract The secular variation rate (SVR) of geomagnetic-field components (horizontal intensity H, vertical intensity Z, and inclination I) shows two types of fluctuations: with a short period (3 ± 0.15 years) and a long period (10–70 years). The amplitudes of the short-period fluctuations (SPFs) were estimated. The SPFs are uniform throughout the Earth, the Z and I SVR fluctuations are synchronous and have the same phases, and H SVR fluctuations are opposite in phase. Modeling of an eccentric-dipole field with a variable axial-pole latitude has shown that the SPFs in SVR are caused by the nutation of the dipole axis (and by the outer-core current systems responsible for the dipole field). LPFs in SVR manifest themselves differently in different regions, and their nature is dominated by the effect of currents in the liquid core near the mantle.