
Accession Number : AD0766241
Title : Geomagnetic Field Models for Ray Tracing.
Descriptive Note : Environmental research papers,
Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS
Personal Author(s) : Wong,Ming S. ; Vanguri,KrishnaSastry ; Friedman,Manfred P.
Report Date : 08 MAY 1973
Pagination or Media Count : 49
Abstract : An accurate geomagneticfield model, consisting of the dipole plus seven higherorder harmonics in dipolar coordinates, is incorporated into a computer program for threedimensional ray tracing. Three options of using magneticfield models are provided: (1) using accurate field in computing both the ray trajectory and the propagationaspect angle between the geomagneticfield vector and the wavenormal vector associated with each point along the ray; (2) using the dipole field for computing rays but using the accurate field for computing aspect angles; (3) using the dipole field for both the rays and aspect angles. Comparisons are made among the results computed, using the three options, in the HF band for a nighttime polar ionosphere and for a noontime equatorial ionosphere. Typical differences of few to ten degrees occur in the aspect angle, for aspect angles near 90 degrees  the value under which geomagneticfieldaligned ionization, if present, would give rise to maximum backscatter of HF waves and thus cause clutter in OvertheHorizon radars. (Author)
Descriptors : (*IONOSPHERIC PROPAGATION, GEOMAGNETISM), MAGNETIC FIELDS, MATHEMATICAL MODELS, ELECTRON DENSITY, HIGH FREQUENCY, COMPUTER PROGRAMS
Subject Categories : Atmospheric Physics
Radiofrequency Wave Propagation
Distribution Statement : APPROVED FOR PUBLIC RELEASE