Solar flares live

Reading a solar flare

A solar flare releases in minutes the magnetic energy stored above a sunspot. The GOES satellite measures the resulting X-ray flux every minute, and that flux defines the flare's class: A, B, C, M then X, each letter ten times the previous one. A C2.3 is 2.3 × 10⁻⁶ W/m²; an X1 exceeds 10⁻⁴ W/m².

The X-rays reach the Earth in eight minutes and abruptly ionise the upper atmosphere on the day side: short-wave radio degrades for about an hour, and the Earth-ionosphere cavity changes shape, which sometimes shows on the Schumann resonance. M and X flares also herald, two or three days later, the coronal mass ejections that shake the magnetic field.

The chart's axis is logarithmic, with the five classes as background bands. Since the feed carries no archive, this page's history starts when Ultrastats began collecting.