A Solar Proton Event occurs when high-energy protons, ejected from the sun's surface during a solar flare, get caught by the Earth's magnetic field and cause ionization in the ionosphere. The effect is similar to auroral events, the difference being that electrons and not protons are involved. The events typically occur where the Earth's magnetic field is lowest, at the north pole, south pole, and South Atlantic magnetic anomaly. The more severe proton events can cause widespread disruption to electrical grids and the propagation of electromagnetic signals.