Auroras have been tingling across the night sky the past few weeks. In Maine, we’re just far enough north to catch their usual southernmost extent. By all accounts this spring, though, they’ve been brighter and bigger.

A couple of things go into this strange and awe-striking phenomenon.

Auroras are spawned by the sun generating streams of electrically charged atomic particles called the solar wind. Some of the particles moving earthward get trapped in the Earth’s magnetic field, where they tend to flow toward the poles. As they interact with other particles, energy is released, giving rise to arcs of colored light, stupendous to our eyes, slowly bending and twisting across the sky.

The peak times for auroras tend to be March and September. Around the vernal equinox (March 20 this year), the Northern Hemisphere reaches the halfway point between its full tilt away from the sun in December and its full tilt toward the sun in June. Tension develops between the Earth’s north-pointing and south-pointing magnetic fields, opening fissures in the magnetosphere (the region of space dominated by the Earth’s magnetic field). Solar wind particles flow into these “equinox cracks,” developing “rope-like magnetic connections” that channel more particles toward the magnetic pole, making auroras about twice as likely as at other times. The same thing happens around the autumn equinox, the halfway point between June and December.

Another factor this year is the sun is reaching the most active phase of its sunspot cycle. Flares, prominences and ejections of material — essentially, colossal explosions — take place pretty frequently on the sun, generating those streams of particles. Some of the explosions are associated with sunspots, which increase and decrease in frequency over 11-year cycles. It happens that the sun is approaching the height of Solar Cycle 25 now. (This is the 25th cycle since the first formal study was made starting in 1755.)

More sunspots, more activity, more auroras here on Earth.

The causes of the eruptions are in general not understood well enough to predict when they’re going to happen. When larger events occur, the astronomers can forecast possible effects, including auroras. Sometimes the explosions on the sun are so huge the flow of particles can disrupt radios and electric grids on Earth. Solar storms in the past have spiked radiation in our region of space to levels that could kill astronauts. In March 1989, a huge solar storm induced ground currents that collapsed Hydro-Québec’s power grid and blacked out 6 million people’s electricity. A solar superstorm in 1859, nicknamed the Carrington Event, overwhelmed Earth’s magnetic field and shorted out telegraph wires, causing fires. Auroras were seen as far south as Cuba, according to NASA. A storm of comparable enormity blew through Earth’s orbit in July 2012. Luckily, the Earth was in another part of its round at the time.

I haven’t gotten out to see the auroras this year, but in the past I’ve seen them, huge snakes of polar green kindling like ice and fire around the Great Bear. They’re unutterably beautiful, and incredibly strange. They twist and seem to shimmer blue and violet, then fade away, like thoughts. Then reemerge.

What would you have made of an aurora before there was a scientific explanation about invisible energies and forces?

Thoughts different from those you think now, no doubt. But the awe, the feeling of stupendous transparent beauty, would no doubt kindle just as it does now, twisting and shimmering on the northern sky of your soul.

Dana Wilde lives in Troy. You can contact him at dwilde.naturalist@gmail.com. His book “Winter” is available from North Country Press. Backyard Naturalist appears the second and fourth Thursdays each month.

Copy the Story Link

« Previous

Backyard Naturalist: Climate change reports

Next »

Backyard Naturalist: Strange lights in the sky