Analysis of magnetometer data using wavelet transforms

Geomagnetic field-line resonances may be identified via the use of cross-phase analysis of data from two closely spaced meridional ground-based magnetometer stations. It has been demonstrated that preprocessing of the data using a wavelet-based filter, chosen with regard to the variance of coefficients of the wavelet components, can be used to remove both low-frequency trend and large amplitude, localized structures, thus facilitating the selection of the eigenfrequency. We demonstrate that the dependence of the variance of coefficients on the wavelet level during a geomagnetic storm event is characteristically different from that obtained from data on a day associated with quiet geomagnetic activity. This suggests that the spectral nature of magnetic disturbances excited in the magnetosphere is dependent upon the level of geomagnetic activity.