Solar flares can cause compasses to malfunction by disrupting Earth's magnetic field.

Solar flares and Coronal Mass Ejections (CMEs) release billions of tons of magnetized plasma into space. When these particles reach Earth, they interact with the magnetosphere, the protective magnetic bubble surrounding our planet. This interaction causes a geomagnetic storm, which is a temporary disturbance of the Earth's magnetic field measured by the Disturbance Storm Time (Dst) index.During a severe storm, such as the famous Carrington Event of 1859, the magnetic field fluctuations were so intense that compasses became completely useless for navigation. Modern researchers at institutions like NOAA and NASA monitor these 'Space Weather' events because they can shift the magnetic north perceived by sensitive instruments. A significant CME can cause the local magnetic field to deviate by several degrees in just a few minutes.The physics involves Faraday's Law of Induction, where the moving magnetic fields from the Sun induce electrical currents in Earth's atmosphere and crust. These induced currents create their own local magnetic fields that oppose or distort the natural field that compasses rely on. While modern GPS uses satellites, these signals are also degraded by ionospheric changes during solar flares, making magnetic backups equally vulnerable.