Spectacular auroras may light up US skies tonight due to geomagnetic storm: Which states can see the northern lights?

Skywatchers in the US could be in for a treat this week, with the northern lights expected to be visible from several states as a geomagnetic storm continues to batter the Earth.

NOAA's Space Weather Prediction Center has issued a G3 (strong) geomagnetic storm watch for October 2, which significantly increases the chances of seeing the northern lights much farther down south than usual.

Several states in northern US are likely to witness the spectacle, weather and light pollution permitting:

• Alaska
• Idaho
• Maine
• Michigan
• Minnesota
• Montana
• New York
• North Dakota
• Northern Illinois
• South Dakota
• Washington
• Wisconsin

That said, auroras are erratic, and people watching from states within the view line will require cloud-free skies, a clear view northward, and conditions with minimal light pollution to catch a clear view.

Some tips for viewers hoping to catch what could be a spectacular display:

- Head far away from city lights, to a place with minimal to no light pollution

- Find yourself a northward-facing view with a clear horizon, devoid of obstacles

- Look up at the night sky around midnight to 2 am local time

- Keep your patience: auroras often come in waves and may appear faint at first before becoming more starkly visible

How are auroras born?

The Sun constantly ejects a stream of tiny particles we call the solar wind, from which the Earth is protected thanks to its magnetic field.

When solar wind particles slam into the Earth's magnetic field after completing the 150-million-km journey from the Sun, some particles get trapped in the field and are funnelled towards the North and South Poles.

These trapped particles then slam into atoms and molecules like oxygen and nitrogen in the upper atmosphere, which begin to glow to release the extra energy, creating the dancing lights of auroras.

The colours that can be seen in auroras depend on which is being 'excited' by solar wind particles: oxygen gives off green and red lights while nitrogen glows blue and purple.

How do geomagnetic storms affect auroras?

Geomagnetic storms occur when the Sun witnesses major activity, like a solar flare or a coronal mass ejection, which send out massive and super-fast clouds of solar wind particles.

This stronger and faster solar wind, in essence, means a larger number of particles colliding with the Earth's atmosphere, which 'powers up' auroras making them visible much farther from the poles than is usual.