Shock-associated clouds move faster than the other two types, which are basically slow flows. The magnetic pressure inside the clouds is higher than the ion pressure and the sum is higher than the pressure of the material outside of the cloud. This implies that the magnetic clouds were expanding even at 1 AU, and the average expansion speed is estimated to be of the order of half the ambient Alfven speed.

Using hour-averaged data from the Helios and Voyager spacecraft, we have investigated the origin and evolution of lewfrequency interplanetary fluctuations from 0.3 to 20 AU.

These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

The magnetic field and plasma data collected by the Voyager spacecraft between 1 and 11 AU are used to study the properties of interplanetary MHD fluctuations and to attempt to answer several related questions about the

Data from ISEE 3, Helios A, and Helios B were used to identify the components of two compound streams and to determine their configurations. (A compound stream is a stream which has formed as a result of the interaction of two or more distinct fast flows.) In one case, ejecta containing a magnetic cloud associated with a disappearing quiescent filament were interacting with a corotating stream. In the second case, ejecta containing a magnetic cloud associated with a 2B flare were overtaking ejecta from a different source. Each of these compound streams produced an unusually large geomagnetic storm, on April 3, 1979, and on April 25, 1979, respectively. The largest geomagnetic storm in the period 1968–1986, which occurred on July 13, 1982, was associated with a compound stream. Thirty geomagnetic storms with Ap > 90 occurred between 1972 and 1983, and there are interplanetary magnetic field and plasma data for 17 of these events. The data suggest that most large geomagnetic storms are associated with compound streams and/or magnetic clouds.