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Physics department continues research in Antarctica

December 10, 2019

IceCube
Surujhdeo Seunarine and UWRF physics student Grace Zeit arrive at McMurdo Station in Antarctica. (Photo courtesy of Surujhdeo Seunarine)

UW-River Falls is involved in two experiments in Antarctica.

Surujhdeo Seunarine is a physics professor who specializes in neutrino astrophysics and theoretical particle physics. Seunarine has taken students with him to the South Pole to work on neutron monitors, where the IceCube project resides as well.

Seunarine explained the neutron monitors and the IceCube detector as “two experiments we work on, on two completely different scales.”

The IceCube is a cubic kilometer detector, buried about 1.5 kilometers deep in the 10,000-foot-thick ice of Antarctica. It is comprised of kilometer long tubes containing digital optic sensors, which function to detect subatomic particles called neutrinos.

Neutrinos have no electric charge. The small size and neutral charge of these particles leaves them unaffected by magnetic fields and other forces like that. They travel in a straight line, and hardly interact or collide with anything, according to Seunarine.

Because light slows down in ice, the speed of neutrinos in the ice is faster than light in the ice. If a neutrino collides with another particle, its energy is converted into light. Deep in the ice of the south pole, where it is dark and transparent, the light travels a great distance. The detectors might observe one or two particles of light. The IceCube collects about a terabyte of data per day. Some of that data is sent north for staff and students here to analyze and study.

When neutrinos are detected, their trajectory can point to where they came from, which leads to figuring out what event produced them. According to Seunarine, the neutrinos that some are most interested in are very high energy, likely to have come from outside of the galaxy.

Since neutrinos rarely interact with other particles, they’re hard to observe.

“They’re rare events in our detector,” Seunarine said. “These are interesting because there are many things we’d like to study with these neutrinos. One of the things is, we’d like to be able to tell where they come from. There’s this long-standing mystery about where these particles, this radiation from space we call cosmic rays, where do they come from?”

“The hope is that if we could observe these neutrinos, we could tell that they come from some external galaxies, that we can look back and see where they came from, have an idea of what’s producing them. Because our physics models or theories tell us that the same things out there that produce these cosmic rays, radiation, that we don’t know where it’s coming from, should produce neutrinos. And if we can tell where the neutrinos come from, we can tell where this other radiation comes from,” said Seunarine.

Neutrinos could even help scientists get a better understanding of what’s called dark matter. Seunarine explained, “Dark matter is what appears to be missing matter in some places in the universe. You look at galaxies and see how they behave, and you find that they’re behaving as if there’s more stuff there than we can see.” Seunarine continued, “There are some theories that say neutrinos can be produced by dark matter particles, when these dark matter particles decay, or collide with each other.”

Work that is happening right now with the IceCube involves what the physics department calls the “IceCube extension.” They are making the detectors more sensitive in order to capture lower-energy neutrinos.

“We do see thousands and thousands of other neutrinos, that are also of interest. We use those for different analyses,” Seunarine said.

The neutron monitors are a different experiment going on at the South Pole. Neutrons, according to Seunarine, are tiny particles produced when particles from outer space hit Earth’s atmosphere. The neutron monitors, sensitive to solar activity, observe cosmic rays, radiation from space. It gives us information of how solar activity influences that radiation.

“The neutron monitors are located at the South Pole for a specific reason: because of the magnetic field structure of the Earth, the cosmic rays that come from outer space are more likely to get to the polar regions – north pole and south pole – unaffected much by the Earth’s magnetic field.” Seunarine continued, “That’s one of the reasons, for example, why we see auroras close to the North Pole and South Pole, because that’s where the energy particles from the sun get to the Earth without getting swept back up back into space.”

Auroras are not the only effect of those energy particles. Every 11 years, the sun’s magnetic field flips its north and south poles. During that flip, there is heightened solar activity, and more destructive solar events.

“Solar storms: what the sun does once in a while,” Seunarine said, “is eject some of the matter of the sun in the form of particles. They just speed through the solar system, and if they’re energetic enough they can reach the Earth. And those particles can interfere with the currents in electronic devices.”

When students go to Antarctica, they perform a variety of activities. There’s basic maintenance to be done on the detectors to make sure they’re operating correctly and will continue doing so for the next year. They do updates on the computers that collect data. One student has been working on electronics for the IceCube extension, testing optical fibers for their light-collecting efficiency.

There are heaters that keep the neutron monitors at a constant temperature, because, as Seunarine explains, “the temperature fluctuates so much between summer and winter there, from absolutely freezing to extremely freezing.” When they open the front of the neutron monitors to test the heaters every year, they end up needing to use their fingers without their gloves on.

UWRF oversees the education and outreach program of IceCube. This involves a range of things including: research projects for undergraduates; 10-week paid summer internships which include a week of astrophysics boot camp in Madison; and Research Experience for Undergraduates, where 6 students from across the US, outside of River Falls, are chosen to work on research projects here.

“The projects the students work on at the pole are designed for students to do. That’s part of the education component of our project. Swapping out electronics, doing special data runs for us to understand the neutron monitors a little bit better, each year we do checks on the components that keep the neutron monitors on a platform outside the south pole station,” Seunarine said.

“There are lots of other things happening at the pole, so we try to find things for them to do that does not involve our project, just to experience some other aspects of the pole; such as helping the meteorologists with these weather balloons for example; it’s not a big thing, you just go out and you let it go, but they participate in it. We try to give them a broad, as broad as we can, experience of science in this extreme place.”

Doing research projects may sound like hard work, but it is also truly rewarding. Seunarine described how doing research projects “helps [students] engage with the university in a different way. They engage with their professors in a different way. They see the department become like their workplace, rather than the place they come to listen to us talk.”

Further, he talks about how it helps students with other academic work and gives them experience that can help them get a job or get into grad school. He encourages students, “not just here in physics, but across the university, to try to get involved in research, and try to get involved early. It’ll change the university experience.”

Anybody can follow the astrophysics research adventures, including those at the south pole, at i3uwrf.wordpress.com. To find more information about IceCube, visit icecube.wisc.edu or uwrf.edu/PHYS/IceCube.