Two examples of magnetic clouds with double rotations observed by the Ulysses spacecraft

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Abstract
A survey of Ulysses magnetometer data has been carried out between Oct 1990 (launch) and Apr 2003 (just after the second northern polar pass) cataloguing magnetic cloud (MC) signatures, i.e., a smooth magnetic field rotation and enhanced magnetic field magnitude. After confirming that each of these events was a true MC by checking for a low proton temperature signature, it was possible to fit a constant α, force‐free flux rope model to each event. This allows parameters describing the global magnetic field configuration of the event in the region of the intersection with the spacecraft's trajectory to be determined. The survey has shown that associated with many MC field rotations there is a second, less well‐defined, rotation. Usually this rotation is so poorly defined that it is impossible to fit the flux rope model to it. However, in two specific cases, presented here, it has been possible to produce good model fits to both rotations. This gives insights into the chirality and relative orientations of the two flux ropes, assuming that is what they are. The results suggest that the two rotations are part of the same, deformed, rope through which the spacecraft has passed at two different points.

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