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HindustanTimes Thu,31 Jul 2014

Life and Universe

NASA rocket blasts into gleaming aurora
ANI
Washington, February 22, 2012
First Published: 15:15 IST(22/2/2012)
Last Updated: 20:37 IST(22/2/2012)

A team of scientists on Saturday night launched an instrument-laden, two-stage sounding rocket arcing through shimmering green aurora, 186 miles above Earth.

The precision measurements from the 40-foot Terrier-Black Brant rocket’s instruments will shed new light on the physical processes that create the northern lights and further our understanding of the complex sun-Earth connection.

The rocket sent a stream of real-time data back before landing some 200 miles downrange shortly after the launch.

AuroraInstruments onboard, including those built at University of New Hampshire’s Space Science Center, sampled electric and magnetic fields as well as charged particles in Earth’s upper atmosphere (ionosphere) that get sloshed back and forth by a specific form of electromagnetic energy known as Alfven waves.

These waves are thought to be a key driver of “discrete” aurora – the typical, well-defined band of shimmering lights about six miles thick and stretching east to west from horizon to horizon.

According to Marc Lessard, an associate professor at the UNH Institute for the Study of Earth, Oceans, and Space (EOS) and department of physics, the Alfven resonator is a structure in the ionosphere that acts like a guitar string when “plucked” by energy delivered by the solar wind to Earth’s magnetosphere high above.

“The ionosphere, some 62 miles up, 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 can get a fundamental frequency and other ‘harmonics’ along the background magnetic field sitting above the ionosphere,” Lessard said.

The Alfven resonator is a narrow, confined area of space – a channel that is perhaps several hundreds of miles tall but only six miles wide.

It is hypothesized that energy from the sun accelerates a beam of electrons producing aurora and also increasing the overall electrical conductivity within the channel.

Understanding how the ionosphere participates in providing the downward current is a critical component of understanding magnetosphere-ionosphere coupling.

“The process turns on an auroral arc and then these waves develop on both sides of the resonator moving up and down. That’s the theory and it appears to be valid, but there’s never been any really good measurement of the process in action. That’s what MICA is all about,” Lessard said.

Magnetosphere-Ionosphere Coupling in the Alfvén resonator (MICA) will provide insight into these wave-driven aurora specifically, but Lessard noted there are other types of aurora that are initiated by different processes and these, too, were investigated at ground-based stations during the MICA launch by scientists, including Allison Jaynes and Ian Cohen, both Ph.D. students working with Lessard in the Magnetosphere-Ionosphere Research Laboratory at EOS.

“It’s all about understanding how the energy of the solar wind gets coupled to Earth’s magnetic field and eventually gets dumped into the our upper atmosphere,” Lessard said about the significance of continued investigation into auroral processes.


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