Wednesday the 20th of March 2019 seemed like just another pretty quiet day on 28 MHz with just a handful of FT8 signals heard on the band. This morning however while I had the radio on in the background monitoring the FT8 frequency of 28.074 MHz, I noticed a sudden increase in the background noise level. It wasn't huge but it was enough that I made of note of the time....11:20am (11:20 UTC).
Later I checked the SolarHam website and sure enough, there seems to be a spike around that time as can be seen on the chart above.
The 1-minute chart shows the peak in more detail...
This graph pretty much matches what I heard.... a rapid increase in the background hiss lasting a few seconds followed by a gradual decline that lasts tens of seconds.
I guess I can never be 100% certain that it was solar noise that I heard but it seems pretty likely.
Addendum : Just for reference...
1) I was using a vertical half-wave antenna about 4m above ground level.
2) The solar flux for today is 70 and the sunspot number is 13.
Update : From SpaceWeather.Com
EARTH-DIRECTED SOLAR FLARE (UPDATED): Northern spring began with a bang. On March 20th at 1118 UT, new sunspot AR2736 exploded, producing a C4-class solar flare that lasted more than an hour.
The explosion sent minor waves of ionization rippling through Earth's upper atmosphere and caused a shortwave radio "brownout" over southern parts of Europe and all of Africa. Anomalies in radio propagation at frequencies below 20 MHz might have been noticed by, e.g., mariners and ham radio operators.
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