A powerful geomagnetic storm lit up the skies over much of northern China on Friday night and Saturday morning with stunning auroras of varying hues. The geomagnetic storm will affect communications and GPS navigation in many areas of the country, but is generally not expected to affect human health. It will continue through the weekend. According to space weather experts, geomagnetic storms are a phenomenon in which the Earth's magnetic field is violently disturbed by high-speed coronal ejection material carrying the sun's magnetic field.