Accession Number : ADA130168

Title :   Sources of Surface Magnetic Field Variability.

Descriptive Note : Final rept.,


Personal Author(s) : Olson,W P

PDF Url : ADA130168

Report Date : 28 Apr 1983

Pagination or Media Count : 44

Abstract : The contribution of non-ionospheric currents to the quiet daily variation in the earth's surface magnetic field (the sub Sq variation) is being reexamined. It has been found that the direct use of magnetospheric magnetic field models to represent the contribution of these currents to the surface field produces large errors. Thus direct integration over the currents was used. The induction problem was addressed and the contribution to sub Sq from currents induced in the earth's crust was determined. The total day to night contribution to sub Sq was found to be a minimum of 12 nanotesla. This contrasts with a measured variation of from 20 to 45 nanotesla. Thus the magnetospheric currents produce from about 1/4 to over 1/2 of the observed pattern. The Birkeland currents also contribute to sub Sq at sub-auroral latitudes. A study was initiated to examine the day to day variability in sub Sq using ground based magnetometer data and direct (satellite observations) of the solar wind. A means for experimentally determining the baseline for sub Sq (and the main field) was developed. (Author)

Descriptors :   *Geomagnetism, *Magnetic fields, Surface waves, Diurnal variations, Graphs, Earth crust, Magnetosphere, Models, Solar wind

Subject Categories : Geomagnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE