Ocean-generated magnetic field study based on satellite geomagnetic measurements: 1. An error reduction technique for gridded data

Abstract

A data set of approximately 28 months of geomagnetic measurements, made by the CHAMP mission, is planned to study the ocean-generated magnetic field. An obstacle for using these data is the large statistical error associated with data averaging in each grid point of the regular grid. The error is 10 2-103 times larger than the magnitude of the ocean-generated signal. Here, a technique designed to reduce this error that is based on a solution of the Laplace (Helmholtz) equation, is proposed. The main idea behind the technique is that the magnetic potential in free space obeys the Laplace equation while, in general, the statistical error does not. The approach allows a reduction of the error in the gridded data over several orders of magnitude and makes the data useable for studying the ocean-generated magnetic field. As a preliminary result for using the data for inferring the ocean-generated magnetic field, the density function is introduced and computed. The function's plot demonstrates the presence of major large-scale ocean current systems within the midlatitudes. Copyright 2011 by the American Geophysical Union.