Long-period magnetic fluctuations and mantle electrical conductivity estimates

摘要: Most attempts to use the worldwide magnetic fluctuations study earth's conductivity structure have been concentrated on 24-hour variations and storm transients. Some of these results inconsistent, possibly because ocean effect complex mode variations. Longer-period fluctuations, considered be due modulations storms, are less subject difficulties. Spectral analyses station data made in an attempt find such The 11-year produce too few vertical distinguished from internal general noise level, but strong signals were obtained at 13.5-day periods some as long 6 months. Mantle profiles tested relation data, K. McDonald model appears quite adequate depth sampled by frequencies.