National Radio Science Meeting, January 5–8,1993, URSI Meeting F3-8, Boulder, CO, 1993

Polarized Transmission and Emission in the Middle Atmosphere (25–150 km) Near the Zeeman-Split Microwave O2 Lines

Hans J. Liebe; George A. Hufford; Michael G. Cotton

Abstract:

Gaseous atmospheric attenuation and delay properties in the 50 to 75-GHz band and near 119 GHz are dominated by the fine structure lines of molecular oxygen. With increasing altitude the complex refractivity displays spectral patterns which change from an unstructured band to the isolated shapes of about 35 lines. The earth's magnetic field (22 – 65 µTesla) splits each line into many sublines. The anisotropic nature of these Zeeman components causes polarization discrimination and Faraday rotation.

The "Zeeman-effect" Propagation Model ZPM estimates the path transmission and emission that originates between 25 and 150 km near isolated O2 lines. Many aspects of how polarized, plane radio waves propagate through a spherically stratified model atmosphere are evaluated (i.e., complex refractivity tensor, path-specific attenuation rates, Faraday rotation, polarization, and optical depth). Related to the absorptive line properties is thermal emission. The example below shows emission near the 61.150-GHz line frequency, as seen by a linearly polarized (HL/VL) pencil-beam antenna looking from outer space into the atmosphere to minimum heights of 65 and 90 km above sea level at either the equator or the north pole. Radiometers of limb-sounding experiments conducted from space platforms (e.g., UARS-MLS and ATLAS-MAS) are able to detect such emissions features, which reveal information on O2 density, ambient temperature, and pressure.

For technical information concerning this report, contact:

Michael G. Cotton
Institute for Telecommunication Sciences
7205527970
mcotton@ntia.gov

To request a reprint of this report, contact:

Lilli Segre, Publications Officer
Institute for Telecommunication Sciences
(303) 497-3572
LSegre@ntia.gov

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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