Ionospheric Modification with Obliquely Incident Waves: Electron Heating and Parametric Instabilities
Abstract
Nearly all ionospheric modification experiments have been carried out with the modifying wave at vertical incidence. For many applications, however, the modifying wave would probably be at oblique incidence. This report identifies nonlinear phenomena tha could be caused by obliquely incident modifying waves. It concentrates on phenomena that might enhance or degrade the performance of high frequency (HF) radar or communications systems. The nonlinear processes that lead to ionospheric modification divide naturally into two categories: (1) ohmic heating, which alters temperature and hence, reaction rates, collision frequencies, and particle densities, and (2) generation of parametric instabilities, which causes a myriad of phenomena. As the incidence angle is increased, heating is affected by two competing trends. It is weakened by the increased path length, but is strengthened near caustics. A transmitter with a power-gain product on the order of 10 MW can launch and oblique wave strong enough to produce electric fields of several tenths of a volt per meter or more in the ionosphere. Such fields produce substantial temperature increases, which are initially concentrated near the caustics, but spread via heat conduction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1985
- Accession Number
- ADA162603
Entities
People
- C. R. Warber
- E. C. Field Jr.