UW Creates Its Own Little Sun

The Big Red Ball is a three-meter-wide hollow sphere that houses a powerful magnet and a series of probes. Jeff Miller

A team in the UW–Madison Department of Physics is using a Big Red Ball to study solar phenomena from the comfort of Earth.

Built in 2010, the Big Red Ball is a three-meter-wide hollow sphere that houses a powerful magnet and a series of probes. When pumped with helium gas that is then ionized into plasma and charged with an electric current, it renders a near-perfect re-creation of the plasma activity and electromagnetic fields of the sun. The device was recently used to study solar winds that result from the Parker spiral, the sun’s magnetic field.

“We asked ourselves, ‘If we have a little magnet — kind of like a magnet you would stick to your fridge, only really strong — if we put that inside of a plasma and spin it around, can we generate this magnetic field?’ And we were able to do that,” says Ethan Peterson MS’15, MS’17, PhD’19, lead author of the study.

According to Peterson, while satellite missions can study microscopic elements of solar activity, the Big Red Ball allows for investigation on the larger scale. To study the actual sun, astronomers would have to send off satellites. But satellites are tiny in comparison to solar wind. The Big Red Ball gives scientists a miniature version of the sun, allowing them to examine plasma behavior from a different viewpoint.

Peterson says the Big Red Ball can also be used to study the sun’s internal magnetic field, as well as plasma around black holes, shock physics, and magnetic reconnection, which causes solar flares and auroras.

The experiment is now funded by the Department of Energy as a National User Facility, which allows outside collaborators to come use it.

Published in the Winter 2019 issue