AN/PRC-160 and AN/PRC-163 Radio Operations and Antenna Theory Practice Test

SID happens when a solar X-ray flare suddenly increases ionization in the dayside ionosphere, causing a temporary HF blackout. The sun’s energy must be present to drive that ionization, so this phenomenon occurs during daylight and ends when the flare subsides and the ions recombine. Because the flare’s duration and the recombination time set how long the absorption lasts, the outage typically spans from a few minutes to several hours. It isn’t limited to seconds, nor does it extend for days or weeks, which are durations associated with longer-lasting geophysical events rather than a transient solar flare-induced disturbance.