Amplitude-Frequency Characteristics of Geomagnetic Noise at Low Frequencies

The features of the geomagnetic noise distribution over frequencies in different bandwidths and in the signal accumulation mode are investigated. It is shown that the amplitude of geomagnetic noise, measured by a magnetomodulation magnetometer in the passband of 0.1 to 230 Hz at the latitude of the Middle Urals in a quiet geomagnetic field can vary from 0.2 to similar to 2 nT from peak-to-peak, depending on the time and place of the measurement. The conditions for measuring a weak magnetic field against a background of geomagnetic noise and the limitations associated with the random nature of the changes in the amplitude of geomagnetic noise and the lack of correlation of its amplitude at various measurement points are considered. The obtained data can be used to estimate the amplitude of a weak external magnetic field, which can be recorded in an undisturbed geomagnetic field in unshielded space, which is of interest in magnetobiology and biomedicine.