A recent geomagnetic storm produced stunning aurora displays over northern China, lighting up the starry sky. The appearance of an aurora results from a fascinating interaction between solar activity and Earth's magnetic field. Starting at 8 a.m. on Wednesday, a geomagnetic storm was detected, with the real-time global geomagnetic activity index (Kp) reaching as high as 9. The geomagnetic storm was mainly triggered by a solar eruption that occurred on Monday afternoon. A coronal mass ejection (C