Interplanetary magnetic flux ropes observed by the pioneer venus orbiter

Interplanetary magnetic field data from the Pioneer Venus orbiter (PVO) were surveyed for five and a half years from December 1978 through May 1984 in search of interplanetary magnetic flux ropes near the Venus orbit. As a result, twenty-six well-defined flux ropes were found which have characteristics similar to those of flux ropes observed near Earth. In one case where the Sun, Venus and Earth were closely aligned, an almost identical structure was observed by the PVO and the Earth-orbiting spacecraft with a time delay of about 36 hours. This observation provides evidence that the structure of interplanetary magnetic flux ropes is maintained during propagation at least from 0.72 AU to 1 AU. A list of the 26 flux ropes identified is presented for future studies such as comparisons with observations of coronal mass ejections.