CHU on 7,850 kHz

Following on from the 3,330 kHz observations described in my previous post, over the past 10 days I have been recording the signal strength of the 7,850 kHz carrier from CHU. All of the individual 24-hour UT periods are shown here...

The curve for 2019-03-05 obviously stands out from the rest but none of the usual solar-terrestrial indices show anything unusual for that day.

The average curve for the entire period, shown below, differs substantially from the VOACAP prediction for the same path but at the most general level they do compare favourably. Both show peaks when one end of the path is in darkness and the other is in daylight and both show the signal to be much weaker when the entire path is in darkness than when the entire path is illuminated by the sun.

On February 28th and March 1st the A index was above 20 but the curves for those two days are not conspicuously different from the others. Whatever differences they may have from the average are minor compared to the unexplained event on March 5th.