Ionospheric Modification by High-power Radio Waves


Book Description

Powerful, high-frequency radio waves have been used to temporarily modify the ionosphere. Thermal and parametric interactions have led to a diverse range of observed phenomena, including generation of density striations and artificial spread-F, enhancements of electron plasma waves, production of extrathermal electron fluxes and enhanced airglow, modification of the D-region temperature and densities, wideband signal attenuation, and self-focusing and scattering of the electromagnetic waves. The physics of ionospheric modification by high-power radio waves is reviewed in the context of our current theoretical understanding; disturbance generation mechanisms are qualitatively described. In addition, results of recent experiments are summarized in which ionospheric irregularities are generated and their evolution and decay processes investigated in detail. The effects and potential controlled applications of these HF ionospheric modifications for various RF systems studies are discussed. The C3I scientific community provides an important motivation for these ionospheric modification studies; their increased interaction and active participation in experimental design and interpretation are encouraged.







Ionospheric Modification by Chemical Releases and High Power Radio Waves


Book Description

Ionospheric plasma density irregularities can be produced locally by chemical releases from space vehicles or remotely by a beam of high power radio waves transmitted from the ground. F-region plasma modification occurs by (1) chemically enhancing the electron number density, (2) chemically reducing the electron population, or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) can determine the effectiveness of ionospheric chemical releases and high frequency electromagnetic wave transmissions in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density and high power radio waves heat the electrons to yield enhanced transport from pressure gradients in the heated region. Subsequent processes, however, can lead to enhanced transport in chemically modified regions and modified reaction rates in the regions affected by high power radio waves.




Preliminary Investigation of Ionospheric Modification Using Oblique Incidence High Power HF Radio Waves


Book Description

A special experiment was carried out using a high powered transmitter and a high gain rhombic antenna to heat the ionosphere at a distance of 1300 km from the transmitter. A Digisonde ionospheric sounder was located at the midpoint to sense any changes that might occur in the ionosphere at the heating cycle period of ten minutes. The measured phase data was processed using spectrum analysis in an attempt to detect this ten minute period. The results are not conclusive but there is some indication that the heating period was detected only during the nighttime in agreement with theoretical prediction. Keywords: Ionosphere; Modification; High frequency; Propagation.













Ionospheric Modification


Book Description







Opportunities for High-Power, High-Frequency Transmitters to Advance Ionospheric/Thermospheric Research


Book Description

Opportunities for High-Power, High-Frequency Transmitters to Advance Ionospheric/Thermospheric Research is the summary of a workshop convened by the Space Studies Board of the National Research Council in May 2013. The request for this workshop was informed by the sponsors' awareness of the possibility that tight budgets would result in the Department of Defense's curtailment or even termination1 of support for the High Frequency Active Auroral Research Program (HAARP), which includes the world's highest-power and most capable high-frequency transmitter - "heater" - for ionospheric research. Although the workshop was organized to consider the utility of heaters in upper atmospheric research in general, it had a specific focus on the HAARP transmitter facility, which is located in a remote part of southeastern Alaska. Research conducted by the ionospheric modifications community - a community that uses high-frequency transmitters to inject energy in the ionosphere and measure its effects using ground and space-based diagnostics - is focused on understanding the interaction of radio waves with the ionospheric plasma, the local consequences of heating in the ionosphere, and studies of non-linear plasma physics processes. The workshop provided a forum for information exchange between the comparatively small group of scientists engaged in programs of upper atmospheric research using high-power high-frequency radar transmitters and the larger ionospherethermosphere-magnetosphere research community. This report examines the state of the art in active ionospheric and thermospheric research; considers the fundamental research areas in ionospheric science that can be addressed using high-power high-frequency-band transmitters; discusses emerging science questions that might benefit from active ionospheric experiments in the sub-auroral zone; and considers ways to combine similar facilities to perform global ionospheric science. The report also examines research opportunities that might arise from the relocation of the AMISR incoherent scatter radar from the Poker Flat Research Facility in Poker Flat, AK to Gakona, AK, the location of the HAARP facility.