Prominences are among the most beautiful of solar phenomena. They are the analogues of clouds in Earth’s atmosphere, but they are supported by magnetic fields, rather than by thermal currents as clouds are. Because the plasma of ions and electrons that makes up the solar atmosphere cannot cross magnetic field lines in regions of horizontal magnetic fields, material is supported against gravity. This occurs at the boundaries between one magnetic polarity and its opposite, where the connecting field lines reverse direction. Thus, prominences are reliable indicators of sharp field transitions. (The fields are either up or down; tilted fields are ...(100 of 10740 words)