Magnetic fields can be hard to understand or characterize. Two natural means of visualization are the aurora and the Sun's corona. In the laboratory, Michael Snyder and Jonathan Frederick of Murray State University in Murray, Kentucky, have explored a novel way to visualize fields. They start with a Hele-Shaw cell, comprising
two parallel glass plates with the narrow gap between them filled with a
ferrofluid--a colloidal dispersion of 10nm ferromagnetic particles. In this image, a Hele-Shaw cell formed from circular glass windows, oriented facing the camera, is illuminated by a white light source behind and to the right of the cell. Within the cell,
the light is scattered by the ferrofluid particles in the high-field region near the poles of three magnets behind the cell. Blue LEDs along the rim of the cell provide background illumination.