Scientists classify the severity of solar flares according to
the amount of X-rays they emit, known as X-ray flux. The GOES
satellite measures the X-rays coming from the sun at any given
time—see the graph of live data below. Looking at this graph,
you can easily identify flares as sharp spikes—the higher the
spike, the larger the flare. A spike that reaches up into the
zone marked 10-5 or higher is likely to have effects here on
earth. Spikes that don’t reach this high are generally
inconsequential flares. Use the horizontal scale (Universal
Time) to figure out when the flare happened. The data on this
graph are automatically updated every five minutes.