"News about the USAP, the Ice, and the People"
United States Antarctic Program United States Antarctic Program Logo National Science Foundation Logo

Image of the sun.
Photo Credit: NASA
This is an image of an extremely powerful solar flare event that occurred in 2003. The image reveals hot gas in the solar atmosphere in false color, and the flare is the bright, white area on the right edge of the sun. The McMurdo CosRay Observatory detects secondary particles created when primary cosmic rays from the sun hit Earth's atmosphere. The observatory can help scientists predict so-called magnetic storms that can disrupt satellites and power grids.

50 years and counting

Cosmic Ray Observatory longest running experiment in McMurdo

Print Entire Article

The U.S. Antarctic Program’s External U.S. government site longest running experiment, which helps keeps an eye on the activity of the solar system’s hottest object, will soon be working in the cold.

The McMurdo Station External U.S. government site Cosmic Ray Observatory first started counting the charged subatomic particles that bombard the Earth in 1960. Fifty years later, the array of neutron detectors operates much as it did then.

“What we’re really doing is measuring the intensity of the cosmic rays hitting the atmosphere, more or less directly above the instrument,” explained Paul Evenson External Non-U.S. government site, co-principal investigator on the CosRay experiment from the Bartol Research Institute External Non-U.S. government site at the University of Delaware External Non-U.S. government site, during a visit to the instrument this past austral summer.

The Bartol Research Institute, under well-known physicist Martin A. Pomerantz, installed the CosRay experiment at McMurdo Station. He had overseen the installation of a similar observatory three years earlier at Thule, Greenland.

In 1960, en route to McMurdo to visit the instrument for the first time, Pomerantz learned that both observatories had recorded a major solar flare event from the sun. It was the first time a solar cosmic ray event had been observed at both ends of the Earth.

Photo Credit: Peter Rejcek
The CosRay building on the road to Scott Base from McMurdo.

“The subsequent story is just wonderful. A lot of things happened because we had that station,” Pomerantz later said during an interview in May 2000 as part of the Polar Oral History Project External Non-U.S. government site conducted by the American Polar Society External Non-U.S. government site and the Byrd Polar Archival Program of The Ohio State University External Non-U.S. government site. Pomerantz passed away in 2008 External U.S. government site.

However, the CosRay experiment lives on, even though the questions posed by today’s researchers have evolved.

“We’re finding new ways to use the data. We’re finding new instruments to use the data with,” Evenson said.

Counting on a prediction

So what exactly are cosmic rays and why are scientists interested in them?

First, cosmic ray is a bit of a misnomer — a holdover term from the early 20th century. Cosmic rays are energetically charged subatomic particles, originating from processes on the sun or from even more mysterious phenomena, such as a supernova explosion.

These cosmic rays speed toward the Earth at nearly the speed of light. The particles that hit the Earth, called primary cosmic rays, are destroyed when they hit the atmosphere, producing a cascade of secondary subatomic particles, including the neutrons that are detected by the CosRay Observatory.

Neutron Monitor
Photo Credit: Peter Rejcek
One of the three neutron monitor units.

The McMurdo observatory is one of a dozen that make up an international neutron monitoring network External Non-U.S. government site called Spaceship Earth, which also includes a neutron station at the South Pole, which was first installed in 1964 (and has since been relocated twice around the U.S. research station there).

By counting the number of neutrons that arrive at these detectors, researchers can calculate how many cosmic rays arrived at a corresponding location in the Earth’s upper atmosphere.

“The main thing we’re observing is the magnetic field that comes out of the sun,” Evenson explained. “Fluctuations in the magnetic field coming out of the sun translate into the intensity of the particles we see.”

Today’s global network of neutron monitors allows the researchers to see the various asymmetries in the sun’s magnetic field. “By looking in different directions, you get a much more complete picture of the magnetic fluctuations,” he said.

Monitoring solar activity and cycles helps scientists predict when magnetic disturbances from the sun might occur. Energetic bursts from the sun can help cause “storms” in Earth’s magnetic field that can disrupt satellites. A major magnetic storm in 2003 affected 47 satellites, including one scientific satellite costing $640 million, which was written off as a total loss. 

“You can gain an idea, by studying the cosmic rays, about what might be coming,” Evenson said.1 2   Next