# Accession Number:

## AD0668332

# Title:

## EXCITATION OF HYDROMAGNETIC WAVES IN THE EARTH'S UPPER ATMOSPHERE BY SOURCES OF FINITE EXTENT,

# Descriptive Note:

# Corporate Author:

## TEXAS UNIV AUSTIN ELECTRICAL ENGINEERING RESEARCH LAB

# Personal Author(s):

# Report Date:

## 1968-04-01

# Pagination or Media Count:

## 85.0

# Abstract:

A boundary value problem based on a model of the earths upper atmosphere is posed, formulated and solved. A point source is included within the stratified model thus necessitating a full three-dimensional treatment. This is often an unnecessary complication if one can assume incident plane waves, current sheets, or other sources infinite in extent. By formulating the problem in circular cylindrical coordinates, symmetrys are maximized and double integral inversions are avoided. Due to the earths static magnetic field, the ionospheric media are anisotropic and the wave equation reduces to a dyadic Helmholtz equation. Seto 1964 has shown this equation to be separable in cylindrical coordinates under certain conditions. This important contribution by Seto is reviewed, somewhat extended, and adapted to the problem at hand. The separation equations lead directly to a dispersion relation. Electromagnetic field ratios sometimes called wave impedances for an EH ratio are derived for an incremental cylinder wave. The boundary condition requirements are satisfied for the layered media numerically by using computational matrices. The advantages and limitations of this method are described. This is followed by a discussion of the contour used in the numerical evaluation of the integral. The vertical inhomogeneities in electrical parameters encountered in the ionosphere are quite severe. To accurately represent a continuously varying medium with a series of homogeneous layers each layer must be relatively thin in terms of wavelength.

# Descriptors:

# Subject Categories:

- Plasma Physics and Magnetohydrodynamics
- Radiofrequency Wave Propagation