Evidence for extreme divergence of open field lines from solar active regions

The paper investigates the structure of the open magnetic field lines that emerge from solar active regions into interplanetary space. The data are based mainly on the measured sizes, positions, and polarization of Type III and Type V bursts, and on electron streams observed from space. It is found that the observations are best interpreted in terms of a strongly diverging field topology, with the open field lines filling a cone of 60 deg.