A Survey and Analysis of Normal Ionospheric Absorption Measurements Obtained from Radio Pulse Reflections
Abstract
An analysis of published midday absorption data obtained by the reflection method of vertical incidence sounding quantitatively establishes the existence of an equatorial absorption anomaly. This anomaly is the abnormally large variation of the amplitude of the seasonal variation observed at equatorial latitudes. It is suggested that certain D-region dynamical processes cause this anomaly. In addition, the analysis disclosed the unexpected existence of a significant latitudinal variation of absorption not due to the cos"x variation; the order of magnitude of this latitudinal variation is of the same order as the variation of absorption due to the sunspot cycle. This latitudinal variation, together with the latitudinal variation of the E-layer critical frequency, indicates that the electron producing mechanisms for the lower ionosphere vary systematically with latitude and solar activity. For middle latitudes, the analysis reconfirmed results obtained previously by other authors. The total variation of lower ionosphere absorption is separated into the four categories: (1) seasonal variation with latitudinal effects, (2) latitudinal variation, (3) solar cycle variation, and (4) winter anomaly effects. Empirically derived formulas are given which permit the calculation of each of these four variations and also the calculation of the total lower ionosphere absorption losses of HF radio waves propagating via the ionosphere both at vertical and at oblique incidence.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1970
- Accession Number
- ADA638023
Entities
People
- Larry D. Schultz
- Roger M. Gallet
Organizations
- Institute for Telecommunication Sciences