Next year the Sun enters the most active phase of its 11-year cycle. ESA is establishing a worldwide chain of monitoring stations to give a ringside seat to see how this solar activity affects our upper atmosphere, and assess the consequences for satellite navigation and communications.

ESA’s Monitor project will track changes to Earth’s ‘ionosphere’, a shell of plasma towards the top of the atmosphere.

Its sensor station network is being set up in advance of the next solar maximum, predicted for mid-2013.

“The current Monitor network is still being developed but has already been detecting mild ionospheric storms,” said Roberto Prieto-Cerdeira, heading the project.

Monitor stations work by measuring variations in GPS signals with greater accuracy than existing systems.

“We are placing sensor stations around the globe, but the vicinity of the equator is a particular focus of interest,” added Roberto. “It exhibits much more dynamic behaviour than the mid-latitudes.

“So we have established stations at Cape Verde off West Africa and Malindi, Kenya, on the other side of the continent.

“In addition, through a deal with French space agency CNES, we will have access to stations hosted by existing tracking sites at Libreville, Gabon and Ascension Island in the mid-Atlantic, the latter site being where the magnetic equator diverts from the geographic equator.

“Further sensor stations under consideration are Maspalomas in the Canary Islands and Kourou in French Guiana.

“Stations in Kevo and Sodankylä in the Arctic, provide high-latitude coverage.”

Ionospheric influences

Sun's impact on the ionosphere

Earth’s atmosphere is made up of onion-like layers. The ionosphere is a layer of electrically charged particles strongly influenced by the Sun, discovered by 20th-century radio pioneers who bounced long-wave radio signals off it.

With the coming of the Space Age, radio signals started passing through the ionosphere to and from orbiting satellites.

Today, everyday life is more reliant than ever on space systems – although the current generation of satellite navigation technology has never experienced a ‘solar max’.

The ionosphere becomes most turbulent as the Sun’s warming thickens it, and then again in the evening as cooling leads to turbulence – including the production of ‘plasma bubbles’ – with the greatest dynamic change around Earth’s magnetic equator.

The effect on radio systems includes signal delay – an important detrimental factor for satnav, where ranging is based on timing accuracy of a billionth of a second – and signal-scattering ‘scintillations’ that render the signal unstable.