Transequatorial HF Radio Observations of Bottomside Structure

Abstract:

Great progress has been made recently in resolving the mystery of
spread F (depletion) formation in the post-sunset equatorial ionosphere. Key
drivers such as the bottomside F region plasma density gradient and its
time-evolving spatial structure are detectable some hours prior to sunset and
have been used to initialize physics models with great forecast success.
However, these observations have relied on expensive assets such as spacecraft
and high-power large-aperture (incoherent scatter class) radars. We present
a inexpensive passive system that relies on emitters of opportunity to observe
the spatial and temporal evolution of the bottomside F region. Doppler and
imaging results will be presented as well as summaries initial analysis of
the first ~9 months of observations in the Central Pacific sector between
Hawaii and American Samoa.