Ionospheric Modification (IM) experiments using the recently completed High-Frequency Active Auroral Research Program (HAARP) HF ionospheric heater located in Gakona, AK, verified the potential of IM in exploiting triggered ionospheric and magnetospheric processes that take advantage of their potential as active media. The research result opened the road to potential applications including new modes of ELF/VLF as well as HF/VHF/UHF communications, over-the-horizon radar, and radiation belt control. The fixed location, size and cost of current ionospheric heaters, such as the HAARP phased array, and the dependence of HF-ionospheric plasma coupling processes on the inclination of the geomagnetic field restricts the realization of the breakthrough applications revealed by the HAARP experiments. The development of transportable, compact, low cost HF heaters can revolutionize both the research and applications of IM. The paper will present results of a current MURI sponsored by AFOSR, whose objective is to replace the current collection of HF sources with a single, mobile low cost amplifier based on recent developments in HPM technology, metamaterials and active materials.
The MURI involves a science and an engineering task. The science task focuses on understanding the design requirements of the mobile heater as a function of geomagnetic latitude and application. Emphasis is placed on latitudes close to the dip equator and applications that involve artificial ionization, generation of few cm irregularities that can reflect signals with GHz frequency and artificial antennas in the ELF/VLF range. Analysis is based in theoretical/computational techniques extrapolating results of previous heating experiments and laboratory tests using the UCLA/LAPD space chamber. The engineering task addresses system design and requirement issues including amplifier sources and electrically small antennas. Emphasis is placed on Inductive Output Tubes (IOT) at the University of Maryland and- Photo-Conductive Solid State (PCSS) RF Generators at Texas Tech University. Current status and future plans for the MURI project will be presented.