“Conditions in the D region of the ionosphere have a dramatic effect on high frequency (HF) communications and low frequency (LF) navigation systems. The global D Region Absorption Predictions (D-RAP) depicts the D region at high latitudes where it is driven by particles as well as low latitudes, where photons cause the prompt changes. This product merges all latitudes using appropriate displays, and is useful to customers from a broad base that includes emergency management, aviation and maritime users. [more]” (Follow this link to learn to learn more.)
[From: http://www.swpc.noaa.gov/drap/index.html Accessed 16 July 2012]