The Northern Lights could be spotted by British stargazers tonight, aurora experts have suggested, bringing a tinge of green to the skies just in time for St Patrick’s Day .

A coronal mass ejection (CME) earlier this week triggered a severe (G5) geomagnetic storm, prompting forecasters to predict sightings this evening as far south as England.

According to Off the Map Travel , which runs Northern Lights tours, the CME was initially expected to glance the Earth. But, to the surprise of many, magnetometers around the Arctic Circle, which are used to measure the KP index (which indicates how strong an aurora will be), reached nine – the highest possible rating – earlier today. Although this rating has now fallen, it is set to continue at around 7KP this evening, giving Northern Lights hunters a decent chance of spotting the heavenly displays.

AuroraWatch UK amber alert, 2015-03-17 13:53:02UT. — AuroraWatch UK (@aurorawatchuk) March 17, 2015

This suggests that Aurora sightings are possible in “Scotland, northern England and Northern Ireland”.



The aurora borealis fills the sky (M. Scott Moon/AP)

“This is the strongest solar magnetic storm we have had in the last three years which is really exciting for aurora hunters,” said Jonny Cooper, director of Off the Map Travel. “Experiencing the Northern Lights is never guaranteed, however, we would recommend going to an area with as little light pollution as possible and uninterrupted views looking north. All we need now is a break in the clouds.”

The forecast for this evening isn’t hugely encouraging, with cloudy skies expected across much of the country.

A survey earlier this summer suggested that seeing the Northern Lights was the most popular 'must-do' travel experience among Britons.

For more advice on witnessing the spectacle, including the best options in Iceland and Scandinavia, see our expert guide.

What are the Northern Lights?

Displays of the northern lights occur when solar particles enter the Earth’s atmosphere and on impact emit burning gases that produce different coloured lights (oxygen produces green and yellow; nitrogen blue). The scientific term for the lights is the aurora borealis (named after the Roman goddess of the dawn). A similar spectacle in the southern hemisphere is known as the aurora australis.

Where can you see them?

The aurora borealis occurs in an oval doughnut-shaped area located above the magnetic pole. The best sightings are within the “doughnut” (rather than at the pole itself), and away from artificial light and moonlight.

The oval rotates with the sun, and it may grow and shrink in size considerably in only a matter of hours. The most spectacular displays occur in the northern parts of the following areas: the Nordic countries of Sweden, Norway, Finland (including all of Greenland and Svalbard), Alaska, Canada and Russia.

Closer to home, fainter displays of the lights can regularly be seen from Scotland. During periods of “solar maximum”, they have been viewed from southern England.

When to go

Displays of the lights are notoriously unpredictable and cannot be forecast in advance. In the northern hemisphere, the aurora season runs from late September or early October to late March. The lights may be seen at any time during this period, but late October, November, February and March are the best bets.

Displays are governed by an 11-year cycle and are at their most dramatic during times of high solar activity, but sightings can be recorded at any time. It is impossible to guarantee a viewing even during a period of “solar maximum”; if the sky is cloudy, the lights will be concealed.

Read more: Aurora hunting in Finnish Lapland