image: Helioseismology was used to measure the Sun's meridional flow (in miles per hour). This flow controls the evolution of the global magnetic field and the number of sunspots. This material relates to a paper that appeared in the 26 June issue of Science, published by AAAS. The paper, by L. Gizon at Max-Planck-Institut für Sonnensystemforschung in Göttingen, Germany and colleagues was titled, "Meridional flow in the Sun's convection zone is a single cell in each hemisphere."
Credit: MPS (Z.-C. Liang)