Tag Archives: Aurora Borealis

Looking at the Northern Lights

Aurora BorealisThe Auro­ra Borealis—that mys­te­ri­ous shim­mer of light appear­ing some­times in the night sky—is a great thing to con­tem­plate now dur­ing Hanukkah, our Fes­ti­val of Lights, and so close to the Win­ter Sol­stice. You can’t even plan to see the Auro­ra, this huge, oth­er­world­ly phe­nom­e­non, one of the strangest of light events on earth. You just have to show up where it might be seen and hope one will reveal itself.

What is the Auro­ra Bore­alis, any­way? It was named for Auro­ra, the Roman god­dess of dawn, and for Bore­as, the north wind, in the 17th cen­tu­ry, and often just called the North­ern Lights.

Before sci­en­tists teased out the secrets of the North­ern Lights, the Kwak­i­utl and Tlin­git peo­ple of Alas­ka inter­pret­ed them as the danc­ing of human spir­its. The Inu­it peo­ple of Labrador iden­ti­fied them as the torch­es held by spir­its from the true heav­ens beyond the sky, meant to lead new­ly arrived spir­its on the right path­way. The Algo­nquin Indi­ans said that they were the reflec­tion of fires built by the Cre­ator, who retired to the north after he fin­ished his work, kept burn­ing to remind the peo­ple that he still thinks of them.

The sto­ry told by sci­en­tists is just as incred­i­ble. Our sun throws off con­stant small storms of plasma—masses of elec­tri­fied gas eject­ed out from its sur­face. These fly out in all direc­tions on the solar wind. When they get near enough to the earth, they slide across our magnetosphere—the giant elec­tro­mag­net­ic body that sur­rounds us, basi­cal­ly shield­ing us from get­ting too much radi­a­tion from the sun and the cos­mos.

Earth's magnetosphere absorbing solar plasma
Earth’s mag­ne­tos­phere absorb­ing solar plas­ma, still from ani­ma­tion at http://wimp.com/borealisaurora/

Some of the plas­ma is pulled in and sucked toward the north and south poles, where it inter­acts with ele­ments in the stratos­phere. Here’s a great ani­ma­tion show­ing this process.

This inter­ac­tion of par­ti­cles of sun and earth cre­ates the Auro­ra Bore­alis, as well as the Auro­ra Aus­tralis in the south­ern hemi­sphere. A green light show, the most com­mon, means that oxy­gen par­ti­cles have been more excit­ed by the flux of free elec­trons and pos­i­tive ions, at an alti­tude of up to 150 miles. The rarely appear­ing red Auro­ra means it’s hap­pen­ing even high­er than that. Blue or vio­let light shows reveal the involve­ment of nitro­gen par­ti­cles at a low­er alti­tude. Some­times the Auro­ra appears as undu­lat­ing cur­tains, some­times as swirling lines, or mere­ly a soft allover glow. We now have numer­ous images, and even videos tak­en from space, show­ing how globe-span­ning a sin­gle event can be.

Aurora seen from space
Auro­ra seen from space, Wiki­me­dia Com­mons

Have you seen the north­ern lights? I haven’t, but I hope I’ll be lucky enough to see them with my own eyes some­day. It will be a chance for an up-close encounter with an off-world astro­phys­i­cal effect, with­out the need for fil­ters or lenses—a direct expe­ri­ence of the vast elec­tro­mag­net­ic envi­ron­ment around us as it briefly drops into the vis­i­ble realm, to become a stun­ning spec­ta­cle of light in the dark­ness.