A Parameterized Model of X-ray Solar Flare Effects on the Lower Ionosphere and HF Propagation

We present a parameterized X-ray solar-flare effects model relating the physics of radiation transport to the observable impact of solar flares on low-altitude ionospheric absorption of High Frequency (HF) signals. Tunable parameters of time varying flare spectral energy density and characteristic flare temperature provide a novel capability to simulate HF experiments over a wide range of X-ray solar flare behavior. Results from our model are consistent with HF propagation data collected over a period of heightened solar flare activity during 5-7 September 2017, including M and X class solar flares. Our predictions and measurements are compared with results from D-RAP [Akmaev et al., 26 2010] and the Wait VLF-driven model [Wait and Spies, 1964].

Akmaev, R., A. Newman, M. Codrescu, C. Schulz, and E. Nerney (2010), Drap model validation: I. scientific report, https://www.ngdc.noaa.gov/stp/drap/DRAP- V-Report1.pdf, accessed: 2018-04-20.

Wait, J., and K. Spies (1964), Characteristics of the earth-ionosphere waveguide for vlf radio waves, NBS Technical Note, U.S. 300.