Computer model of a geomagnetic storm affecting the Earth's southern hemisphere. Geomagnetic storms occur when eruptions from the Sun's surface send energetic particles toward the Earth. Here colours represent the intensity of the particles interacting with the magnetic field around the South Magnetic Pole in the upper atmosphere. Red is highest intensity, through yellow, green and blue to purple (low intensity). Geomagnetic storms can damage communication satellites and affect power grids. They also create nitric oxide in the atmosphere, a gas that affects the atmosphere's heating and cooling.