Northern lights
Aurora borealis, or northern lights, fill the sky over Finnmark, northern Norway (Reuters)

The European Space Agency has launched three satellites to study the weakening magnetic field on Earth.

The Earth's magnetic field plays a crucial role in supporting life on the planet, shielding the atmosphere from particulate radiation from the sun. Without its magnetic field, Earth would be exposed to dangerously high levels of radiation.

The few particles of radiation that do enter the Earth's atmosphere cause the celestial phenomenon of the aurora lights at both poles.

The satellites are part of the ESA Swarm Project and were launched from Russia's Plesetsk Cosmodrome on a Rockot vehicle, according to Reuters.

They will collect geological data over the next four years to improve scientists' present understanding of the Earth's magnetic field and its seemingly regular changes of polarity.

The Earth's magnetic field is similar to that of a bar magnet tilted 11° from the spin axis of the planet. It is linked to the rotation of the Earth's molten metallic core, and the electrical current that movement generates.

Rock specimens of different ages have different orientations of permanent magnetisation. There have already been about 171 magnetic field reversals over the past 71 million years.

Geological records suggest the magnetic field has reversed on average every 450,000 years, and the last reversal occurred about 800,000 years ago, meaning that another magnetic field reversal could be on its way. Each reversal is thought to take between 1,000 and 10,000 years to complete.

Scientists say the magnetosphere is weakening and may vanish before flipping upside down.

The consequences of a diminishing magnetic field are not known, but for a period life on Earth may be exposed to higher levels of radiation and satellites will be more exposed to solar winds.

Migratory birds may also lose track of set paths during seasonal movements.

"Swarm is an essential mission, not only for Europe but also for the world," Jean-Jacques Dordain, Director General ESA, told Reuters following the launch. "We cannot live on planet Earth without this (magnetic) shield."