Influence of Magnetic Cloud Expansion on Its Fits

Magnetic clouds observed between 1995 and 2003 are fitted using force‐free cylindrical flux rope models. The cloud parameters yielded by a static model are compared with those obtained from a modified model that includes magnetic cloud expansion. The deviations of these fits from measurements are quantified and compared with parameters measured by Wind. The comparison reveals that the model with expansion provides better fits for larger expansion speeds and for magnetic clouds observed close to their axis. We conclude that expansion of magnetic clouds plays an important role in the MC evolution and should be accounted in space weather models.