Rare, mystery blasts from sun can devastate the ozone layer and spike radiation levels on Earth

The remarkable aurora in early May this year demonstrated the power that solar storms can emit as radiation, but occasionally the sun does something far more destructive. Known as "solar particle events", these blasts of protons directly from the surface of the sun can shoot out like a searchlight into space.

Records show that around every thousand years Earth gets hit by an extreme solar particle event, which could cause severe damage to the ozone layer and increase levels of ultraviolet (UV) radiation at the surface.

We analysed what happens during such an extreme event in a paper published Monday (July 1). We also show that at times when Earth's magnetic field is weak, these events could have a dramatic effect on life across the planet.

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Earth’s critical magnetic shield

Earth's magnetic field provides a crucial protective cocoon for life, deflecting electrically charged radiation from the sun. In the normal state, it functions like a gigantic bar magnet with field lines rising from one pole, looping around, and plunging back down at the other pole, in a pattern sometimes described as an "inverted grapefruit." The vertical orientation at the poles allows some ionising cosmic radiation to penetrate down as far as the upper atmosphere, where it interacts with gas molecules to create the glow we know as the aurora.

However, the field changes a great deal over time. In the past century, the north magnetic pole has wandered across northern Canada at a speed of around 40 kilometres per year, and the field has weakened by more than 6%. Geological records show there have been periods of centuries or millennia when the geomagnetic field has been very weak or even entirely absent.

We can see what would happen without Earth's magnetic field by looking at Mars, which lost its global magnetic field in the ancient past, and most of its atmosphere as a result. In May, not long after the aurora, a strong solar particle event hit Mars. It disrupted the operation of the Mars Odyssey spacecraft, and caused radiation levels at the surface of Mars about 30 times higher than what you would receive during a chest X-ray.