Skywatchers in northern England, Scotland and Northern Ireland could see a display of the colourful northern lights on Friday and Saturday nights. The aurora borealis will appear as a faint glow or as shifting veils of light in the sky.

“If the skies are clear it will be worth keeping an eye on the northern sky,” said Jim Wild, a space physicist from the University of Lancaster in the UK.

Any auroras that do occur will appear successively lower in the northern sky the farther south the observer is located. Observers should therefore wait for clear skies and then find a location with an unobstructed view of the northern horizon.

Auroras happen where the Earth’s atmosphere is struck by high-speed particles from the sun.

The northern lights over St Mary’s Lighthouse in Whitley Bay, North Tyneside. Photograph: Owen Humphreys/PA

The current spate of displays have been sparked by a gigantic solar eruption, known as a coronal mass ejection (CME), that collided with our atmosphere on Friday morning at around 1am. Observers in Canada and the northern states of the USA saw mild auroras as a result.

A second ejection will arrive on Friday afternoon and could increase the likelihood of the lights appearing over the UK tonight. The stronger the compression of Earth’s magnetic field the further south the aurora will be seen, and the more active the display.

Double CMEs like this are rare. When they do occur, it is not unusual for the second to have a bigger impact on the Earth’s magnetic field than the first. “It seems that the first CME clears a path, allowing the trailing CME to retain more of its energy,” said Wild.

CMEs themselves are vast bubbles of gas. Often they contain a billion tonnes of matter that was once part of the sun’s atmosphere. They are blasted outwards into space by explosions known as solar flares.

An aurora over Holt in Norfolk. Photograph: Brian Egan/Corbis

The first CME erupted from the sun on 9 September. It was thrown into space by an unusually long solar flare that lasted six hours. A day later from the same location on the sun, a shorter but more powerful flare blasted another CME our way. The second one is travelling faster than the first and is the one that will impact the Earth’s atmosphere this afternoon.

Orbiting spacecraft will measure the strength of the likely disturbance about an hour before it hits Earth.

Based on the currently available data, the US’s Space Weather Prediction Center is reporting that the geomagnetic activity this will cause is expected to be strong tonight and to continue into tomorrow. Such activity is the precursor to the auroras themselves.

An aurora over Seaham in Teesside. Photograph: Jordan Crosby/Alamy

“The chances of enough geomagnetic activity to push the northern lights far enough south to be seen from the UK are higher than usual tonight and tomorrow night,” Wild confirmed.

Email alerts of auroral activity can be obtained by signing up to the University of Lancaster’s AuroraWatch.