Latitude variations and their relation to forced movements of the inner solid core

Abstract

To explain the difficulties involved in the comparison of regular patterns of latitude variations with the model of free nutation of the Earth’s rotation axis, this paper discusses all stages of research, including the request of Kelvin, who asked Newcomb to discover variations with a period of 300 days; the positive answer of Newcomb, who reported the discovery of such a variation (1876); the detailed investigation of Chandler (1891), who established that the 300-day variation does not exist, but there exist variations in monthly averages of latitudes characterized by harmonics with periods of 365 days (a year) and 410–440 days; and the subsequent hypothesis of Newcomb (1892), who suggested that the process of the latitude variation is nevertheless the free nutation and a period of 300 days can be adjusted to a period of 410–440 days. The validity of Newcomb’s hypothesis has not been critically examined in the geophysical and astronomical literature. Therefore, it is not surprising that no progress has been made in elucidating the applicability of the Newcomb model to this interesting global process. The motion of the rotation axis in the body of the Earth and the process of the latitude variation (as is shown in the paper) are accounted for in terms of the variation in the position of the Earth’s center of mass due to forced movements of the inner core. An accurate and comprehensive description of the periodic solar perturbations of the orbital motion of the Earth (Moon) around the Earth-Moon center of mass reveals the complete correspondence of these periodicities to the latitude variation periods.