Why Launch a Rocket Deep into an Aurora?
Man, some scientists sure know how to liven up a Saturday night! On Feb. 18, a NASA-funded collaboration launched a sounding rocket directly into a shimmering green aurora, from the Poker Flat Research Range in Fairbanks, Alaska.
It’s called the Magneto-Ionosphere Coupling in the Alfven Resonator mission, with the aim of studying so-called “space weather” — arising from the stream of charged particles from the sun that mess with the magnetosphere, sometimes interfering with our electronic systems — like the Global Positioning System (GPS) satellites. We would like our GPS to keep on working, and not be knocked out by a solar storm.
The rocket’s instruments collected tons of real-time data as it shot through the display before coming back down to Earth a good 200 miles away. And the scientists got some pretty stunning photographs to boot.
Scientists are interested in studying auroral processes because they could shed light on how energy from the solar wind ends up coupling with Earth’s magnetic field (the magnetosphere), before being summarily dumped into the upper atmosphere. Out of the solar wind’s heartbreak comes our space weather.
There are two types of aurora: diffuse and discrete. With the former, you’ll get a faint flow that might not even be visible at night; with the latter, you’ll see that gorgeous, sharply defined band of colorful light most of us associate with the Northern Lights,or Aurora Borealis.
The MICA mission is especially interested in the discrete aurora, particularly one of the possible underlying mechanisms: Alfven waves, created by something in the ionosphere called the Alfven resonator.
It’s a long narrow channel in space and the same beam of charged particles from the sun that creates the aurora, also boosts the electrical conductivity in the resonator. And this produces Alfven waves. That’s the hypothesis, anyway; MICA’s measurements should help validate it.
Marc Lessard of the Univeristy of New Hampshire’s Institute for the Study of Earth, Oceans and Space, provided a wonderfully poetic analogy for how this works in the UNH press release, comparing the Alfven resonator to a giant guitar string stretching through space:
“The ionosphere… is one end of the guitar string and there’s another structure over a thousand miles up in space that is the other end of the string. When it gets plucked by incoming energy, we get a fundamental frequency and other ‘harmonies’ along the background magnetic field sitting above the ionosphere.”
The musical analogy is particularly apt, because those same charged particles also produce electromagnetic waves at very low frequencies — Nature’s Radio, if you will. Every year, the Minnesota Planetarium’s sound recorder, Steve Greevey, journeys north and records those waves. You can hear the crackles, hisses, and eerie whistles that make up the auroral “voice” in the video below.
Image credits: Ryuho Kataoka, Tokyo Institute of Technology (top) and Lee Wingfield, NASA Wallops.