Quasi-optical Ray Tracing of Gaussian Beams in the Magnetosphere

By Alan Ling

In a recent paper published in JGR Space Physics, AER Senior Staff Scientist Alan Ling applied a method for tracing rays in tokamak plasmas  to tracing rays in the Earth’s magnetosphere.  By appealing to complex geometric optics he addressed the problem of computing power flux from pencil rays using classical geometric optics that occurs when constituent rays exhibit coplanarity. The paper describes the construction of Gaussian beams and the quasi-optical method of tracing such beams.  Examples of tracing Gaussian beams from a ground transmitter, a partial beam, and from a satellite location are presented.  A median method for dealing with nonviable contributions to the power flux from sections of the beam encountering caustics or otherwise experiencing coplanarity  is described.  The effect of beam parameter choices on the resulting power flux computation is provided for each of the examples.

Gaussian Beam image_blog 022123.png
The figure shows the progression of a Gaussian beam quasi-optically traced from a position near the VLF transmitter NAA at nine different times.  The sections of the beam are color-scaled according to the values of2 , the imaginary part of the eikonal function that describes the propagation of the beam

 

Citation:  Quasi-optical Ray Tracing of Gaussian Beams in the Magnetosphere

A. Ling, M. J. Starks, & J. M. Albert

Journal of Geophysical Research: Space Physics, 127, e2022JA030649, 2022

 

 

Sr Staff Scientist, AER