The GOES X-ray plots shown here are used to track solar activity and solar flares. Large solar X-ray flares can change the Earth’s ionosphere, which blocks high-frequency (HF) radio transmissions on the sunlit side of the Earth. Solar flares are also associated with Coronal Mass Ejections (CMEs) which can ultimately lead to geomagnetic storms. SWPC sends out space weather alerts at the M5 (5x10-5 Watts/mw) level. Some large flares are accompanied by strong radio bursts that may interfere with other radio frequencies and cause problems for satellite communication and radio navigation (GPS).

The latest event is the latest X-ray flare automatically detected by the GOES 16 satellite, or manually entered if the detection algorithm fails, without regard to any earlier events.

In other words, the "max" refers only to the maximum (peak) X-ray flux for the particular flare in question; so, even though an M-class event may have occurred earlier, it will be supplanted by the next flare detected, if the subsequent flare is only a C-class event.

The particulars for defining the begin, maximum, and end-time of an X-ray event are:

The begin time of an X-ray event is defined as the first minute, in a sequence of 4 minutes, of steep monotonic increase in 0.1-0.8 nm flux.

The X-ray event maximum is taken as the minute of the peak X-ray flux.

The end time is the time when the flux level decays to a point halfway between the maximum flux and the pre-flare background level.

Sometimes the algorithm will not trigger on a flare with a gradual rise-time (common for limb events), and the forecaster will have to enter the particulars manually.