Fig. 2

GOES15 1-8 Å solar X-ray flux from 2011-02-14 to 2011-02-15. The GOES flare classification is provided on the minor y-axis. The plot also includes annotations of flares exceeding GOES class C5.0, with red vertical lines indicating the flares’ peak time. The example interval also shows that during these two days of intense activity background X-ray flux was high, making it difficult to identify small flares. Notice also that the first two C-class flares peak essentially simultaneously (i.e., within 1 minute from each other).