What are the northern lights?

Whirling aurora

northern lights aurora borealis

Photo: Biletskiy Evgeniy / Colourbox
The northern lights dance across the winter sky at Senja Island in northern Norway.

Ilan Kelman
Agder, Norway

Waves of green and pink whirl above, backdropped by the stars pinned against the dark dome. These magical ribbons commonly grace the high latitudes, yet gazing at them never grows dull.

The first time I watched the northern lights, I penned a poem entitled simply “aurora”:

with terrifying beauty
the sky alight with flame
shimmering and quivering
the soul shan’t be the same

the wispy, haunting tendrils
sear down from up above
remote from their oppression
of life and lore and love

the spirit’s chilled by wonder
its ceaseless awe is pain
this ecstasy of torture
a universe insane

The scientist in me enjoys understanding their cause as much as I enjoy partaking in nature’s art. The northern lights, or aurora borealis, occur for the same reason as the southern lights, or aurora australis.

They begin at our planet’s source of light and life: the sun. Our star unceasingly releases charged particles in a flow called the solar wind, part of wider space weather. Sometimes, a localized eruption or disturbance on the sun’s surface produces a huge burst of particles and energy, termed a solar flare, coronal mass ejection (CME), or other phrases.

No matter how intense this space weather is, a minority of particles reaches the Earth’s surface directly, since a magnetic field surrounding our planet blocks them. Many particles deflect into space. The remainder are ensnared by the magnetic field directing them to the Earth’s south and north magnetic poles.

These magnetic poles are not fixed. They wander around, hundreds of miles from the geographic poles that we call the North Pole at 90°N and the South Pole at 90°S. The lines of the Earth’s magnetic field dip toward the Earth’s surface and then meet at the magnetic poles, permitting the charged particles to enter the atmosphere. The particles collide with molecules and atoms in the air comprising 78% nitrogen, 21% oxygen, and 1% others, such as argon and carbon dioxide.

These collisions heat up the air, so the molecules and atoms emit light. Oxygen gives the aurora’s characteristic green, while pink and related colors are mainly nitrogen—although bright red can indicate oxygen high in the atmosphere. The waltzing is from the charged particles following the ever-shifting magnetic field lines.

Often, it feels as if we can reach out and caress these sky curtains. We would require a long ladder, as the bottom of the lights rarely dips lower than 78 miles above the Earth’s surface. The top can be more than 10 times that distance away.

When the sun’s activity ramps up into a solar storm or geomagnetic storm, the Earth’s magnetic field and upper atmosphere can warp. Then, we learn the dark side of auroral beauty. Enormously intense space weather smashed into the Earth 2,700, 1,250, and 1,030 years ago, presumably producing awesome auroras. This occurred long before we depended on electricity and wireless communications.

The first solar storm to demonstrate its power (pun intended) hit in 1859, wreaking havoc on the new-fangled communications system called the “telegraph.” Named after amateur astronomer Richard Carrington, the Carrington Event is the worst space weather that humanity has yet directly recorded.

Expanding technology augments space weather’s effects. Events in 1940 and 1989 knocked out electricity to swathes of North America. A 2003 solar storm added satellite interference to the list of impacts. On July 2012, a geomagnetic storm almost at the level of the Carrington Event ripped across the Earth’s orbit. Fortuitously, we had passed that spot just seven days earlier.

If we had been slammed head-on, then we might still be recovering today. Imagine trying to repair or replace a significant proportion of the world’s satellites and electricity transformers!

Have we learned to be ready for The Big One? Many electricity, communication, and satellite systems build in protection against space weather including the option to shut down quickly and then, after the storm has passed, to restart. Plenty of our equipment cannot do so and we do not have the capability to swiftly rehabilitate extensive damage, such as to national electricity, internet, and phone grids.

Instead, we might have darkened cities and the time to look up from our phone to enjoy the most spectacular auroras that humanity remembers.

This article originally appeared in the November 2023 issue of The Norwegian American.

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Ilan Kelman

Ilan Kelman is Professor of Disasters and Health at University College London, England, and Professor II at the University of Agder, Norway. His overall research interest is linking disasters and health, including the integration of climate change into disaster research and health research. Follow him at www.ilankelman.org and @ILANKELMAN on Twitter and Instagram.