Source of High Trace-Velocity Infrasound Signals and Pulsating Auroras

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This project investigates the possible association of high trace-velocity signals, observed by infrasound arrays, with the aurora and seeks to establish the sources of the signals. The origin of the proposed study is a 2004 discovery of high trace velocity infrasound signals that appeared to be caused by pulsating aurora. A relatively large data of "high trace-velocity events" and it now seems clear that pulsating aurora may not be the sole source of such signals: while events are observed during pulsating aurora, there are many nights with extensive displays of pulsating aurora but show no signs of the infrasound signals. However, there does seem to be a connection with the level of geomagnetic activity, since many events occurred during times of high activity as recorded by local ground-based magnetometers. No physical process has yet been identified for the cause of these signals and there is not good understanding of the acoustic wave propagation from ionospheric sources. The project will analyze the infrasound data set in conjunction with auroral optical and magnetic data to establish and quantify any relationships between the observed parameters and to identify possible ionospheric sources for the signals. A large infrasonic data set is currently available, which will be complemented by additional events observed by infrasonic arrays; that data acquisition and analysis are funded through a separate program. An important new data element will be provided by the Advanced Modular Incoherent Scatter Radar (AMISR) currently located at Poker Flat Research Range, Alaska. AMISR can provide detailed spatial and temporal ionospheric information which may help in the identification of the source or sources of the infrasound signals. The project will also provide funding for the continued operation of the auroral video camera at the University of Alaska's Geophysical Institute which will provide useful information on auroral dynamics. In addition to the analysis and interpretation of the infrasound signals, the project will undertake a complementary study on the mechanisms by which energy can be transferred into atmospheric acoustic waves and under what conditions the energy transfer occurs. The broader impacts of the project includes the support of a graduate student who will receive training in data acquisition and hardware, atmospheric and ionospheric dynamics and processes, and manipulation, analysis, and interpretation of large data sets. The project will enable improved understanding of ionospheric processes and acoustic wave propagation in realistic atmospheres.