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Kaimbridge

Discrepancy In X-Ray Data?

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On the Solar activity link for 2017-Jan-16, it lists two B-class flares for the day, a B1.3 @01:44 and a B1.4 @18:23, both of which match SWPCʼs Solar Events page for Jan 16.

However, while if you hover over 01:44 on that dayʼs flare graph, it shows B1.31, when you hover over 18:23, it gives a B1.99, both of which match the values for the time slots on the 1-minute X-ray flux text page for Jan 16!

When you look at the graph, it is obvious that B1.99 is the correct value:  chart-1.jpegWhy the discrepancy?

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Hi @Kaimbridge

Looks like you caught NOAA on a mistake ;). It isn't the first time NOAA classifies flares with faulty strength, we've done multiple corrections in the past for the M1+ solar flares where there was difference in the GOES data and the SWPC logs and those where corrected by us in our databases to make sure we have the correct values. We have now edited the flare so it will display correctly, thx for reporting!

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Thatʼs what I figured.  P=)

On a related note, why do they tend to round flare/flux levels down—e.g., “C3.28” “C3.2”, “X1.79” “X1.7” “X1”—rather than to the nearest (in these examples, it should be “C3.3” and “X1.8” “X2”)?

This doesnʼt seem to be an occasional error, but intended policy:  Is there a valid reason for this?

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It's a good question that we also don't have an answer for. SWPC apparently has an policy to round flares always off to the lower value. In normal math an X1.99 would be X2 but SWPC will always say it was a X1.9. Maybe they do this intentionally to prevent that an M9.97 would be classified as an X1

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