Accession Number : AD0617965

Title :   EXTRAPOLATING ELECTROMAGNETIC FIELDS FROM VALUES IN A SPHERICAL REGION.

Descriptive Note : Rept. for Oct 64-Mar 65,

Corporate Author : DIKEWOOD CORP ALBUQUERQUE N MEX

Personal Author(s) : Babb,D. D. ; Granzow,K. D.

Report Date : JUN 1965

Pagination or Media Count : 55

Abstract : Methods are developed for extrapolating electromagnetic fields from values of the spherical harmonic expansion coefficients of the spherical components on a sphere surrounding a source region. The region outside the sphere is considered to be homogeneous, isotropic, source free, and nonconducting, except that application of the method of images allows the introduction of an infinitely conducting ground plane. Solutions of the scalar wave equation are made applicable by expressing the spherical harmonic expansion coefficients of the rectangular components in terms of the coefficients of the spherical components. Two methods are developed for obtaining time dependent solutions for fields at points outside the sphere without invoking Fourier analysis. One method results from inserting the expansions of the rectangular components into the Kirchhoff integral solution of the wave equation. The other method involves eliminating the explicit frequency dependence of the eigenfunction solution of the wave equation by introducing a differential operator to replace the Hankel function. These methods are useful when the source has a very wide-band frequency spectrum, so that it is best described in the time domain. This is the case with electromagnetic pulses from nuclear detonations. (Author)

Descriptors :   (*FIELD THEORY, ELECTROMAGNETIC FIELDS), (*ELECTROMAGNETIC FIELDS, MATHEMATICAL PREDICTION), (*SPECIAL FUNCTIONS(MATHEMATICAL), ELECTROMAGNETIC FIELDS), BOUNDARY VALUE PROBLEMS, INTEGRALS, OPERATORS(MATHEMATICS), PARTIAL DIFFERENTIAL EQUATIONS, ELECTROMAGNETIC PULSES, NUCLEAR EXPLOSIONS, PROPAGATION

Distribution Statement : APPROVED FOR PUBLIC RELEASE