Why are we seeing more Northern Lights this year?

This article was originally published on The conversation. The publication contributed the article to Space.com’s Expert Voices: Editorials and Perspectives.

Solar Cycle 25 kicks off in style. Our sun has a cycle of activity and as it becomes more active there will be more sightings of the Northern (and Southern) Auroras. This is what is happening this winter.

In addition to emitting sunlight, our sun has an expanding atmosphere composed of charged particles and magnetic fields. This high-speed solar wind is blowing across Earth, but Earth has its own magnetic field (imagine a large bar magnet with its poles roughly aligned with geographic north and south) and this can deflect the solar wind. This magnetic barrier is weakest at the poles of the “bar magnet” so we tend to see auroral displays at high latitudes. The larger the space weather storm, the more deeply charged particles can penetrate the Earth’s magnetic field, so that during intense events, the Northern Lights are seen at lower latitudes.

In 2022 we have seen spectacular auroral displays, displays of natural light in the sky in more places than usual across the UK.

Northern lights are also being spotted in northern England this winter, which is a telltale sign of increased solar activity.

Related: Watch the aurora paint the sky above Earth in these stunning astronaut photos and videos

Why is this happening now?

Solar flares erupt from the surface of the sun, and these expand outward as coronal mass ejections that carry energy in both their charged particles and magnetic fields. If a coronal mass ejection collides with Earth, it interacts with the Earth’s magnetic field, causing a geomagnetic storm.

Earth has a roughly dipole magnetic field, with a tail stretched by the solar wind, and with the poles close to the geographic north and south poles, and it is at these high latitudes that charged particles can travel to reach higher easily the earth’s atmosphere.

Charged particles strike the upper atmosphere (ionosphere), causing it to glow, creating a magnificent spectacle, the Northern Lights or Aurora Borealis. These aren’t just beautiful displays. These extreme space weather events can affect a wide range of systems, from power supplies, aviation, satellites and radio communications.

Space weather

These effects can induce unwanted currents in any electrical network, causing damage and, in extreme cases, blackouts. The ionosphere is also disrupted, affecting communications, and further out in space, where the environment of charged particles becomes more energetic, can damage satellites.

The sun has a cycle of activity, in active years solar flares and coronal mass ejections are common, while in calm years they occur rarely. Solar cycles last on average about 11 years but actually vary in both duration and level of activity. It is possible to track the level of solar activity by counting sunspots ⁠—dark spots on the surface of the sun that correlate with the likely occurrence of solar flares. The past few years have been a period of low activity, and solar minimum ⁠—the sunspot number minimum ⁠—was observed in late 2019.

(Image credit: Chapman et Al, Geophysical Research Letters (2020), provided by the author)

We are now in the ascending phase of the new cycle of solar activity, as the number of sunspots observed each day is steadily increasing. We may also see an increase in solar flare activity. There are three categories of solar flares, measured by their X-ray emissions: X-class flares are large; these are major events that can trigger continental-wide radio outages and city-wide power outages. M-class flares are medium-sized; they can cause brief radio blackouts that affect Earth’s polar regions. Class C flares are small with few noticeable consequences here on Earth.

On October 9, 2021, an M-class solar flare erupted sending a coronal mass ejection that hit Earth on October 12, triggering a moderate geomagnetic storm. On November 3-4, we saw the most intense geomagnetic storm to hit Earth since September 2017.

Since each solar cycle is unique in both duration and level of activity, it is difficult to predict how active the next phase of the new solar cycle will be. Recent research has mapped this irregular cycle in time to a uniform solar cycle clock, shown in the graph above.

We can read back from the solar clock to see where (or when) we are in the solar cycle, so in addition to helping tourists plan their northern vacations to see the Northern Lights, this chart could also help power grid operators who need to schedule critical maintenance during periods of quiet weather in space.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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