Under previous NSF funding the PI has developed and successfully demonstrated a remote sensing tool capable of measuring lower ionospheric electron densities over wide geographic regions with a minimum of ground based instrumentation based on radio sounding of very low frequency radiation from lightning strokes. As part of this effort, broadband VLF/ELF data has been recorded at a Duke University site for the last five years. In addition, the group has designed and constructed two portable VLF/ELF sensor and data acquisition systems that have been used in some recent experimental campaigns in Colorado (2005), and Northern and Southern Brazil (2005 and 2006). The thrust of this new research project is to use these existing data sets together with data from new targeted measurement campaigns to provide quantitative estimates of the lower ionosphere electron density variability over a wide range of geographic locations and time scales. The program will pursue a number of specific research goals: 1) measure mid-latitude variability and structure and determine to the degree possible the processes that drive this variability; 2) measure high and low latitude D and E region profiles, with particular emphasis on measurements in the South Atlantic magnetic anomaly region where high energy particle precipitation effects are expected to be especially significant, 3) measure the altitude profiles of different classes of lightning-produced ionospheric perturbations to answer long-standing questions about the mechanisms responsible, 4) measure E region layer variability and spatial structure, and 5) develop the technique into an autonomous distributed instrumentation system that would fit into a distributed instrument array concept. The research is devoted largely to understanding large scale atmospheric variability and its effects, and thus is by its nature closely tied to important societal issues such as global climate change. Graduate as well as undergraduate students will be involved in the research program.
