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

Report Date:

1973-05-08

Pagination or Media Count:

49.0

Abstract:

An accurate geomagnetic-field model, consisting of the dipole plus seven higher-order harmonics in dipolar coordinates, is incorporated into a computer program for three-dimensional ray tracing. Three options of using magnetic-field models are provided 1 using accurate field in computing both the ray trajectory and the propagation-aspect angle between the geomagnetic-field vector and the wave-normal 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 geomagnetic-field-aligned ionization, if present, would give rise to maximum backscatter of HF waves and thus cause clutter in Over-the-Horizon radars. Author

Subject Categories:

  • Atmospheric Physics
  • Radiofrequency Wave Propagation

Distribution Statement:

APPROVED FOR PUBLIC RELEASE