This year we're hearing a lot about coronal mass ejections (CMEs), the spectacular explosions of solar particles that are spewed far into space. Although Earth's magnetic barrier prevents most CME penetration, CMEs can cause extensive damage to electronic communications and to power grids. For this reason, scientists monitor the solar cycles very closely. Dr. Hughes explains how solar cycles and these enormous storms occur, the effect of these ejections on Earth's magnetic field, and a number of other features of space weather. W. Jeffrey Hughes, PhD., Professor of Astronomy and Associate Dean of the Graduate School, Boston University. Dr. Hughes is Director of the Center for Integrated Space Weather Modeling (CISM), an NSF Science and Technology Center. He is an international expert on the dynamics of the Earth's magnetosphere and its interactions with the solar wind and the ionosphere.