Return of a GNSS villain: The ionosphere strikes again

Every 11 years or so, the activity on the Sun reaches a peak. During this solar maximum, which can extend to several years either side of the actual peak, the Earth gets hammered by intense space weather. When storms of particles spat out from the Sun smash into the Earth's atmosphere, the results can be spectacular. They are responsible for breathtakingly beautiful events like the dancing curtains of light known as the aurora (northern and southern lights). But they can also be equally vicious, causing widespread electrical power blackouts and disrupting navigation and communication systems worldwide. In regards to Global Navigation Satellite System (GNSS) observations, the ionosphere is still our biggest villain. The ionosphere is part of the Earth's upper atmosphere and continues to be the single most important error source affecting GNSS observations. This article describes the ionosphere and how it is influenced by space weather. It goes on to discuss the likely effects of the approaching solar maximum (expected to occur in early 2013) on GNSS surveys in Australia. We conclude with the good news that Australian GNSS users should be alert, but not alarmed.