Progressive transformation of a flux rope to an interplanetary coronal mass ejection

DASSO, S.; NAKWACKI, M.S.; DÉMOULIN, P.; MANDRINI, C.H.

Mérida

Congreso; VIII Conferencia Latinoamericana de Geofísica Espacial (VIII COLAGE); 2007

Asociación Latinoamericana de Geofísica Espacial

Magnetic clouds (MCs) are formed by twisted flux ropes that transport an important amount of magnetic flux and helicity, which is released in CMEs. At 1 AU from the Sun, the magnetic structure of MCs is generally modeled by neglecting their expansion during the spacecraft crossing. However, in some cases, MCs present a significant expansion. We present here an analysis of the huge and significantly expanding MC observed by the Wind spacecraft during 9 - 10 November 2004. This MC was embedded in an ICME. After determining an approximate orientation for the flux rope using the minimum variance method, we obtain a precise orientation of the cloud axis by relating its front and rear magnetic discontinuities using a direct method. Our observations are interpreted by considering the existence of a previously larger flux rope, which partially reconnected with its environment in the front.  These findings imply that the ejected flux rope is progressively peeled by reconnection and transformed to the observed ICME (with a remnant flux rope in the front part).