Plots include data from yesterday and today. Check the time (select UTC, 24-hr) to see where the new data is being recorded. There is usually a noticeable discontinuity where the new data ends and the old data remains.
Points are plotted every 10 seconds for 24 hours and the chart is updated every 5 minutes. There are a total of 8,640 points on the graph. (See the new Dataq spreadsheet)
(Based on your computer's clock. Chart displays yesterday's data after time above.)
Black = linear, Red = logarithmic
The plot is from the Oddball Sid Receiver. SIDs will cause spikes between about 12:00 and 0:00, where the plot is normally low. The high portion between 0:00 and 12:00 is nighttime sky wave. The width of the SID window is a function of the season. The logarithmic plot is arbitrarily offset and scaled. The scale is approximately 2 dB per small division.
To confirm a flare, see http://www.swpc.noaa.gov/today.html#xray . For a six hour close-up view, see http://www.swpc.noaa.gov/rt_plots/xray_1m.html.
If the signal drops to zero suddenly, WWVB may have gone off the air; Check the NIST website to confirm.
To show how effective the receiver can be, here's a plot from the Oddball Sid Receiver during a smaller flare. It looks a bit blurred because I stretched it to match the NOAA GOES satellite plot of the same time period (3/10/2012).