The fraction of interplanetary coronal mass ejections that are magnetic clouds : Evidence for a solar cycle variation
نویسنده
چکیده
"Magnetic clouds" (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized by e n h a n d magnetic fields with an organized rotation in direction, and low plasma p. Though intensely studied, MCs only constitute a fraction of all the ICMEs that are detected in the solar wind. A comprehensive survey of ICMEs in the nearEarth solar wind during the ascending, maximum and early declining phases of solar cycle 23 in 1996 2003 shows that the MC fraction varies with the phase of the solar cycle, from 100% (though with low statistics) at solar minimum to 15% at solar maximum. A similar trend is evident in near-Earth observations during solar cycles 20 21, while Helios 1/2 spacecraft observations a t 0.3 1.0 AU show a weaker trend and larger MC fraction.
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