This is to organize a workshop to assess potential future roles of high-power HF (high frequency)-band transmitters in support of ionospheric and thermospheric research. It will focus, in particular, on the Alaskan HAARP (High Frequency Active Auroral Research Program) facility. HAARP is an ionospheric research program jointly funded by the U.S. Air Force, the U.S. Navy, the University of Alaska, and the Defense Advanced Research Projects Agency (DARPA). The key instrument at the HAARP station in Gakona, Alaska is a high-power radio frequency transmitter operating in the HF band, which is used to temporarily excite a limited area of the ionosphere. Historically, the "heater" communities that operate facilities like HAARP have been somewhat distinct from the research communities that study the ionosphere and thermosphere. The ionosphere and thermosphere constitute an important part of the near-Earth space environment where low-Earth orbiting satellites operate and through which communication and navigation signals are being transmitted. The ionosphere-thermosphere (IT) system is, however, subject to several geophysical forcings originating from the Sun. The interaction between the solar wind and the Earth's magnetosphere results in a fraction of the solar wind energy and plasma being transmitted into the magnetosphere, and subsequently into the ionosphere and thermosphere to produce auroras and other geomagnetic phenomena. Solar energetic particles penetrate into the upper and middle atmosphere to cause significant ionization and chemical effects. Solar ultraviolet and extreme ultraviolet radiation is the main source of energy for heating, ionization, and photochemical reactions in the thermosphere and ionosphere. The workshop will provide a useful venue for these communities to meet and to assess the utility and cost/benefits of HAARP in future IT research. Specifically, the workshop will have a major impact on the future of the HAARP facility as the Air Force has announced its intent to step back from its historical commitment to the facility and HAARP users look towards other sources of support, including the NSF. Absent these additional sources of funding, the facility would be closed and the land reclaimed in accordance with agreements dating back to the 1970s when the facility was an military radar site.
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 termination 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. The report is available for free download at: www.nap.edu/catalog.php?record_id=18620 .
