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Oct 11, 2024 · Experts say the Northern Lights, or Aurora Borealis, are more visible right now due to the sun being at what astronomers call the “maximum” of its 11-year solar cycle. What this means is that ...
- Overview
- What are auroras, or the northern and southern lights?
- Why are auroras green, red—and sometimes blue or purple?
- Where can you see auroras?
- When do auroras occur—and are they happening more often?
The aurora borealis and aurora australis have dazzled us in the night sky for centuries. Here’s what causes them—and why we’re seeing them more lately.
No matter how many times you see them, the northern lights, or aurora borealis—and their Southern Hemisphere equivalent, the aurora australis—are an ethereal, breathtaking sight. Dancing silently in Earth’s upper atmosphere, they form iridescent sheets of green and red (or sometimes blue and purple) light.
Italian astronomer Galileo Galilei, coined the term aurora in 1619 after the Roman goddess of dawn—mistakenly believing it to be the reflection of sunlight off the atmosphere.
In fact, both northern and southern lights are caused by the interaction of gases in Earth’s atmosphere with the solar wind: a stream of electrically charged particles, called ions, that shoot out from the sun in all directions.
(Staring at the sun: an interactive look at our dynamic home star.)
When the solar wind reaches Earth, it slams into the planet’s magnetic field, producing currents of charged particles that flow toward the poles. Some of the ions become trapped in a layer of the atmosphere called the ionosphere, where they collide with gas atoms—primarily oxygen and nitrogen—and "excite" them with extra energy. This energy then gets released as particles of light, or photons.
An aurora's colors signify where in the atmosphere, and with which gases, all of this is happening.
For example, it takes almost two minutes for an excited oxygen atom to emit a red photon, and if one atom collides with another during that time, the process may be interrupted or terminated. So, when we see red auroras, they are most likely at the highest levels of the ionosphere, approximately 150 miles (240 kilometers) high, where there are fewer oxygen atoms to interfere with one another.
(Why is the sky blue? Learn about it with your kids.)
In contrast, green photons are discharged in less than a second, so are more common in moderately dense parts of the atmosphere, 60 to 150 miles (100 to 240 kilometers) above Earth’s surface.
Auroras have been observed on every planet in the solar system except Mercury—even, as with Venus and Mars, when the magnetic field is very weak or nonexistent. They have even been detected on a huge “rogue planet” 20 light years away. And astronauts have taken spectacular photographs and video of Earth’s auroras from the International Space Station.
For the more earthbound among us, the best places to see auroras are in the “auroral zone,” between about 60 and 75 degrees latitude, both north and south. You’re even likelier to see an aurora if you’re in a smaller band of Earth between 65 and 70 degrees latitude.
(Here's the best place to see northern lights in the lower 48 states—and how to visit it.)
You also need somewhere where the skies are dark and clear and far from light pollution. In the Southern Hemisphere, that generally means Antarctica, Tasmania, or southern New Zealand in fall or winter. North of the Equator it includes locales such as the areas around Fairbanks, Alaska; Churchill, Manitoba; the Lapland area of northern Sweden and Finland; and Tromso, Norway, among many others.
One good way to predict a strong aurora night is to count forward 27 days from the most recent one; auroras are strongly associated with sunspot activity, and as it takes 27 days for the sun to rotate on its axis, that’s how long it will take an aurora-producing sunspot to show up again.
Some years see more auroras than others. Sunspot activity waxes and wanes on an 11-year cycle; the most recent upward trend began in 2019 and will peak in 2024 or 2025.
Greater sunspot activity is also why there are sometimes aurora displays in parts of the world that otherwise rarely see them. This rise in activity creates a greater likelihood of large solar storms, which can shoot electromagnetic radiation and particles toward Earth; when they hit our atmosphere, they flood it with so many particles that the auroral zone expands far beyond its usual limits.
This effect was most recently in evidence in early 2023, as solar storms resulted in auroras being visible as far south as Arizona and England. In addition to causing dazzling displays, however, these solar storms can also impact power grids and GPS systems.
(Solar storms may throw off whale navigation too.)
Even the most active of sunspot cycles, however, will find it hard to match the largest solar storm on record, however. On September 1, 1859, astronomers had been watching a growing number of sunspots develop on our star’s surface when a solar flare sped toward Earth, creating vivid aurora displays as far south as Cuba and as far north as Santiago, Chile. Having never seen them before, some observers believed the bright lights presaged the end of the world, or that “it appeared as if there was a colossal fire on earth which reflected its flames on the heavens.”
The aurora is not visible during daylight hours. The aurora does not need to be directly overhead but can be observed from as much as 1000 km away when the aurora is bright and if conditions are right. A short term forecast (~30 minutes) along with the last 24 hours of activity can be found on the Aurora - 30 Minute Forecast page. And SWPC's ...
Apr 24, 2023 · CNN —. The breathtaking dancing shimmer of the aurora borealis and its counterpart in the southern hemisphere, aurora australis, dazzles those lucky enough to catch a glimpse of Earth’s ...
Oct 11, 2024 · The northern lights or aurora borealis are visible over the Tappan Zee or Governor Mario M. Cuomo Bridge Bridge on Oct. 11, 2024 near New York City. Photo by Roy Rochlin/ Getty Images
1 day ago · The aurora is a luminous glow frequently seen around the geomagnetic poles of the northern (aurora borealis) and southern (aurora australis) hemispheres. The light is caused by collisions between electrically charged particles streaming from outer space that enter Earth’s atmosphere and collide with molecules and atoms of gas (primarily oxygen and nitrogen).
People also ask
Why do auroras occur in the northern hemisphere?
Where can you see auroras?
Are auroras happening more often now?
What is Aurora Borealis & Aurora Australis?
When do auroras occur?
Where do auroras come from?
May 13, 2024 · Chemical elements there, such as oxygen and nitrogen, become ionized and glow in various colours, creating auroras. The lights are usually seen near Earth’s poles, but on 10 May, because of the ...
