Source of the more geoeffective magnetic cloud of November 20, 2003

SCHMIEDER, B.; PARIAT, E.; CHANDRA, R.; MANDRINI, C.H.

Sorrento

Workshop; 3rd Solar Orbiter Workshop:; 2009

ESA

The more geoeffective magnetic cloud of November 20, 2003,  has been associated with the CME of  November 18, 2003, at 08:50 UT.  The   magnetic cloud has a positive helicity and its mean radial velocity is about 600 km/s.  AR 10501, crossing the central meridian between November 17 and 18, is  believed to be the source region of the halo CME that was observed travelling  at  a velocity of 1650 km/s in LASCO white light images. The global magnetic helicity of AR 10501 is negative; then, the association of the CME with the MC is apparently in contradiction with what we expect from magnetic helicity conservation. However, a detailed analysis of the 2D magnetic helicity flux maps of the AR  shows how an emerging flux of positive helicity progressively built a  region with positive helicity along the southern section of the AR magnetic inversion line. We propose that the  ?flux rope? that is observed later as an MC originates from this localized positive helicity zone. We will also discuss the role of the solar wind reducing the speed of the ejected material.