Mapping cosmic rays in the Southern Hemisphere

South Pole - Researchers waiting for the completion of the IceCube Neutrino Observatory have been mapping cosmic rays in the Southern Hemisphere. They discovered an excess of cosmic rays coming from certain directions in the sky.

The research was presented at the American Physical Society's April Meeting in Anaheim, Calif., Saturday, April 30.

"We have observed that these cosmic rays come preferentially from certain parts of the sky, and this is the first time that such an observation is done in the southern sky," said Marcos Santander, of the University of Wisconsin-Madison. The excess, called an anisotropy, mimics one already observed in the Northern Hemisphere. Santander will speak about their discovery of anisotropies in the southern sky at the April Meeting.

When high energy cosmic rays collide with atoms in the Earth's atmosphere, they produce elementary particles called muons. Though IceCube was built to detect astrophysical neutrinos, it can also detect these cosmic ray-produced muons, finding tens of billions of them each year. Scientists say these high concentrations shouldn't exist and are working to understand their sources. Analyzing this new data may help to determine the origins of these anisotropies.

The construction of IceCube at the geographic South Pole was completed in December. The experiment is designed to use one cubic kilometer of Antarctic ice as a subatomic particle detector of neutrinos or other difficult-to-detect elementary particles.southern sky for anisotropies in the arrival direction of cosmic rays in this energy range. We report on the discovery of a cosmic ray anisotropy over a wide range of angular scales in the sky, which is consistent with anisotropies previously observed in the northern sky by other experiments.