Magnetic clouds with east/west orientated axes observed by Ulysses during solar cycle 23

Abstract

The second Ulysses orbit of the Sun has provided a unique opportunity for the study of the interplanetary manifestation of coronal mass ejections (ICMEs) over a wide range of heliographic latitudes. The Ulysses dataset between July 1995 and mid April 2003 has been surveyed for magnetic clouds (MCs), a subset of ICMEs. As a result of the rising solar activity during this time, ICMEs were observed over a wide range of heliographic latitudes. By fitting a constant α, force-free flux rope model to each event we determine whether the local axis orientation of the MCs are directed in an eastward or a westward sense. We show that during this period in solar cycle 23, those MCs whose hemispheric origin is clear display a trend, with MCs in the southern hemisphere having predominantly westward directed local axes and those in the northern hemisphere having eastward directed local axes.