Observations of medium-scale magnetic ropes in interplanetary space

Interplanetary magnetic clouds, dominated by magnetic ropes with average durations of 20–30 hours, make manifest the expansion and propagation of coronal mass ejections (CMEs) in interplanetary space. Recently, Moldwin et al. reported that they had observed some small-scale magnetic ropes with durations of several tens of minutes, and they believed that the distribution of their scales might be double-peaked. We have made a comprehensive inspection of the data of the satellites WIND (1995–2000) and ACE (1998–2000), and found medium- scale magnetic ropes with durations of several hours. Our preliminary analysis of 28 such cases led us to think that the size distribution of the magnetic ropes in interplanetary space might be continuous. This conclusion may possibly impose an important physical constraint on the origin of magnetic ropes in interplanetary solar wind.