9219360 Egbert This is a program of research to improve processing and inversion methods for geomagnetic observatory arrays. The main goal of this research is to reduce the significant uncertainties in mantle conductivity suggested by the large variation of published models. To accomplish this, historical and recent geomagnetic observatory array data will be used to seek constraints on large scale averages of mantle conductivity. The research involves development and application of two related methods: multivariate statistical techniques for exploratory data analysis and data reduction; and methods for simultaneous inversion of observatory array data for both external sources and Earth conductivity. ***
