Spectral Characteristics of the Magnetic Field During the Matuyama–Brunhes Reversal

Abstract—It is shown that, according to observations, there was a decrease in the amplitude of four axisymmetric harmonics in the spherical harmonic representation of the geomagnetic field during the last geomagnetic reversal. Only the dipole component changed sign at the time of reversal. For all four modes, on an interval of 200 000 years, quasi variations with characteristic times of 10–50 000 years were observed. During the reversal, magnetic variations with characteristic times of 100–1000 years intensified due to destabilization of hydrodynamic flows in the core.