A new NASA sounding rocket mission will soon take to the Alaskan skies. The
LAMP mission, short for Loss through Auroral Microburst Pulsations, will fly
above an often-overlooked kind of northern lights to test a theory on what
causes them. The launch window at Poker Flat Research Range in Fairbanks,
Alaska, opens on Feb. 24, 2022.
The aurora borealis, or northern lights, is a familiar treat to those who
call northern latitudes home. Auroras come in different shapes and colors,
waving their ribbons of vibrant green, red and purple across the sky. But
one variety of aurora displays a peculiar behavior: it pulsates.
“It’s sort of hypnotic, pulsating every few seconds,” said Dr. Alexa
Halford, space scientist at NASA’s Goddard Space Flight Center in Greenbelt,
Maryland, and principal investigator for the mission. “The blobs and colors
remind me of a lava lamp, where you can just sit and stare at it for
hours.”
Like all aurora, pulsating aurora are set alight by electrons (and
occasionally protons) from near-Earth space. These electrons plunge into our
atmosphere and collide with atoms and molecules, causing them to glow in
their distinctive colors – red and green by oxygen, blue by nitrogen – as
they release their excess energy.
But what sets those electrons into motion in the first place? For pulsating
aurora, the going theory points to chorus waves, so named because they were
first detected as audio signals in radio receivers during World War I.
But chorus waves are not sound waves – instead, they move through plasma,
the electrified gas that makes up over 99% of the observable matter in
space. They ripple through the particles trapped within Earth’s magnetic
environment, shaking some loose to fall into our atmosphere.
“Chorus waves occur at exactly the right frequency to ‘resonate’ with the
electrons that create pulsating aurora, similar to how you pump your feet at
just the right time to get a swing to go higher and higher,” said Dr.
Allison Jaynes, space physicist at the University of Iowa in Iowa City and
co-investigator for the mission. Eventually, some of these electrons “jump
off” the swing – and shoot into our atmosphere.
Chorus waves can launch both low and high-energy electrons, which may
explain some puzzling coincidences. Pulsating aurora are caused by fairly
low-energy electrons, but they’re often observed alongside flashes of X-ray
light known as microbursts, which come from higher energy electrons.
“Pulsating aurora and microbursts seem to happen at similar times, even
though they’re different energy ranges,” Halford said. “So, the big question
is, are they the same events? Are they being driven by the same processes in
the magnetosphere?”
That’s what LAMP hopes to find out.
The LAMP instrument will fly aboard a sounding rocket, a small rocket
launched into space for a targeted few minutes of measurements before
falling back to Earth. Watching ground-based cameras at the Poker Flat
Research Range and at a downrange site called Venetie, the team will wait
until they see auroras start to pulsate. Then it’s go time.
The rocket will fly above the pulsating aurora, measuring the low energy
particles that cause them as well as the medium- and high-energy electrons
that should also come from a chorus wave. On the ground, a riometer will
provide an independent measure of high energy electrons, so the rocket team
can confirm their measurements.
The only thing they won’t measure is the chorus wave itself, though the team
is hoping for a chance flyby of a satellite that could potentially provide
those observations.
“We have all but one piece of the puzzle that we’re hoping to catch
simultaneously…but any of it is going to provide us new information and
hopefully help us test that theory that it’s the chorus waves behind it
all,” Halford said.
The LAMP mission is an international collaboration with contributions from
NASA’s Goddard Space Flight Center, Dartmouth College, University of New
Hampshire, and University of Iowa, and Japan Aerospace Exploration Agency,
Tohoku University, Nagoya University, and Kyutech in Japan.
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Space & Astrophysics