Investigation of Near-Earth or Ionospheric Modification of Pulsating Auroras

SCIENCE

M. Jason Ahrns

For stargazers of the northern hemisphere, seeing a bright and multicolored aurora dance in the night sky is a given. Most of us don't question it, we simply marvel and enjoy the light show. Others however, like scientist Michael Jason Ahrns, ask the big questions. (click on photo for more of this story)

Ahrns studies the aurora – specifically,  the “pulsating” aurora. A pulsating aurora is often seen late at night and marked by its variations in brightness, seeing large sections get brighter and dimmer over a matter of seconds. Ahrns is on a quest to discover where pulsating auroras originate within Earth's magnetosphere.

Ahrns, a PhD candidate in space physics, has researched the aurora for the past three years. He became interested in the pulsating aurora after realizing that while it accounted for a large portion of auroral activity, it was a little researched subject.

The topic of pulsating auroras caught Ahrns interest after results published in 2012 discussed “very fast pulsations” which, at first glance, seemed to be “too fast” to account for within existing models of measurement. The pulsating aurora is understood to come from very high altitudes near the Earth's equatorial plane, but the 2012 study suggested an origin much closer to Earth. “I decided to see if I could create a model that would give a more firm estimate on where some of the pulsating aurora may originate,” he said.

Ahrns research is helping scientists understand how energy is transported from solar wind into Earth's upper atmosphere. This knowledge can help predict 'space weather' events that impact modern infrastructure, including power grids. Ahrns is also focusing on how particles behave in the region where most satellites operate. This research could prevent future damage to said satellites.

According to Ahrns, the “big take-away message” is that his research strongly suggests a process or processes operating far closer to Earth than originally thought. While it's very likely many pulsating aurora originate at the equatorial plane as suspected, many do not. Ahrns added that he sees his research as an addition rather than a replacement to the original hypothesis.

“I think the long-reaching impact of my research will be an understanding that the pulsating aurora isn't as well understood as previously thought,” he said.

Despite a passionate interest in the science behind the aurora, Ahrns still marvels at it. “I'm an observational guy first and foremost,” he said. Ahrns has spent many a night spent at the Poker Flat Research Range, often until until 2 or 3 in the morning.

“Some of the aurora I'd see on those nights was really spectacular,” he said. “When it would coincide with one of Poker Flat's rocket launches, [it was] just amazing.”
 

Pulsating Aurora is a common type of auroral form typically seen in the hours after midnight where patchy, extended regions of auroral emissions rise and fall in intensity on the scale of seconds. Though it's one of the more common types of auroral activity, it has inspired a comparatively small amount of research when compared to the brighter and more dynamic discrete arcs of the earlier auroral substorm stages. While the discrete aurora certainly has a higher rate of energy deposition into the ionosphere, it is also fairly short lived and confined in spatial extent. The diffuse and pulsating aurora, on the other hand, generally covers a much larger spatial and temporal extent, and therefore actually represents as much or more total energy input into the ionosphere than the discrete aurora, possibly from 50% to as much as 80% of the total auroral energy input (Meredith 2009). Though a theoretical model based on wave-particle interactions exists for the generation of pulsating auroras, observations, particularly those enabled by more recent instrumentation, cast doubt on the universality of the model. This suggests one or more poorly understood mechanism/s, more Earthward than the standard model, that produces or modifies the transport of particles and energy from the magnetosphere into the ionosphere, and on into the neutral atmosphere.

Profile

Name: M. Jason Ahrns, Graduate Student

Institution: University of Alaska Fairbanks

Mentor: Donald Hampton, dhampton@gi.alaska.edu

Award: Research Grant

Funding Period: 2014