A Study of the Long-term Trends in the US Mid-latitude Ionosphere from 1936-2009 by Extending the US Ionospheric Database Two Decades Prior to the 1957 IGY

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This goal of this project is to investigate the long-term behavior of the mid-latitude ionosphere near Washington, D.C., using historical ionosonde measurements obtained from 1936 to 1957 in order to extend existing data by more than two decades prior to the 1957 International Geophysical Year (IGY), when ionospheric observation became widespread. The archival data is currently stored on 35 mm films, and the first goal of this effort is to digitize the records using a film scanning device to be developed for this project. The data will be converted into ionospheric state parameters (electron density profiles) using an automated procedure, the Expert System Ionosonde Reduction (ESIR), previously developed by the investigators. The new data set will be analyzed in conjunction with an existing database of hand-scaled ionogram values, obtained from an ionosonde located near Washington, D.C. (1957-1968) and Wallops Island (1967-2009), in order to assess long-term trends in the ionospheric parameters. A specific scientific focus of the trend analysis is the quantification of secular cooling of the upper atmosphere, an outstanding question in aeronomy. The new, extended dataset will be made available to the wider community.