Solar flares and geomagnetic storms can significantly impact the ability to commicute on the medium and high frequency (300 kHz - 30 MHz bands). Solar flares cause radio blackouts due to collisional absorption from enhanced D-region ionization, especially on the lower frequencies. Geomagnetic storms can cause large-scale depletions of ionospheric densities that can reduce the maxium usable frequency (MUF) on a global scale. These impacts can be observed in large-scale amateur radio networks such as the Reverse Beacon Network, WSPRnet, and PSKReporter.
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- Frissell, N. A., Vega, J. S., Markowitz, E., Gerrard, A. J., Engelke, W. D., Erickson, P. J., et al. (2019). High-frequency communications response to solar activity in September 2017 as observed by amateur radio networks. Space Weather, 17, 118– 132. https://doi.org/10.1029/2018SW002008.