Case study on low-frequency time-code signal during the 10–15 November 2025 geomagnetic storm: observations and analysis
Xiaohui Li
IntroductionGeomagnetic storms are typical solar eruption activities. When high-speed solar wind or coronal mass ejections from solar eruptions strike the Earth, they trigger rapid severe geomagnetic disturbances and further induce ionospheric variations. For low-frequency time-code signals that depend on the ionosphere as a reflective propagation medium for long-distance transmission, geomagnetic activities degrade the signal signal-to-noise ratio, cause signal attenuation and phase delay, and