A solar flare is like a tightly coiled spring suddenly uncoiling. In the Sun's corona, energy accumulates in the twisted magnetic field, and then it is abruptly released, accelerating particles and heating plasma. But seeing exactly how the magnetic field itself changes during a flare is rare: it requires special observations.

In October 2022, astronomers tracked an X1.1 flare that occurred on the visible side of the solar disk. Using microwave radiation, they mapped the magnetic field above the active region and followed its evolution. They found that at several points above the tops of magnetic loops, the field weakens at an enormous rate — up to 10 gauss per second. For comparison, Earth's magnetic field at the surface is about 0.5 gauss, so in one second, a field twenty times stronger than Earth's disappears at these points.

The magnetic field was also measured at the footpoints of the loops and in the lower part of the erupting prominence. The three-dimensional models of the flare built from these data largely matched the observations, although they revealed some discrepancies. The main conclusion: during the rise phase of a solar flare, the coronal magnetic field indeed decays, and the released energy is sufficient to power all other manifestations of the flare — from plasma heating to radiation fluxes.

Thus, the spring of solar activity, compressing and uncoiling, reminds us time and again: even a star has moments when it releases accumulated tension.