A magnetic cloud as a distended flux rope occlusion in the heliospheric current sheet

A magnetic cloud was detected both near Earth by IMP 6–8 and 30° of longitude away from Earth by Pioneer 11 at 4.8 AU. The nearly identical magnetic signatures at the two spacecraft imply that its radial dimension increased little between them. The magnetic field within the cloud rotated from toward to away polarity, marking sector boundary passage at both locations. Interpreted in terms of a flux rope, its axis was highly inclined to the ecliptic plane, implying that its cylindrical cross section in the ecliptic plane was distended by at least 30° of longitude, forming an extensive occlusion in the heliospheric current sheet. A similar magnetic signature was observed at the same sector boundary by Pioneer 10 at 6.1 AU, at a longitude between Earth and Pioneer 11. Its radial dimension, however, was diminished by a factor of 3. We suggest that it was the same cloud, compressed by a second, oncoming transient that was observed behind the cloud at 1 AU.