Relationship between earth-directed solar eruptions and magnetic clouds at 1 AU: A brief review

We review relationships between coronal mass ejections (CMEs), EIT post eruption arcades, and the coronal neutralline associated with global magnetic field and magnetic clouds near the Earth. Our previous findings indicate that the orientation of a halo CME elongation may correspond to the orientation of the underlying flux rope. Here we revisit these preliminary reports by comparing orientation angles of elongated LASCO CMEs, both full and partial halos, to the post eruption arcades. Based on 100 analysed events, it was found that the overwhelming majority of halo CMEs are elongated in the diection of the axial field of the post eruption arcades.Moreover, this conclusion also holds for partial halo CMEs as wellasfor events that originate further from the disk center.This suggests that the projection effect does not drastically change the appearance of full and partial halos and their images still bear reliable information about the underlying magnetic fields.We also compared orientations of the erupted fields near the Sun and in the interplanetary space and found thatthe local tilt of the coronal neutral line at 2.5 solar radii is well correlated with the magnetic cloud axis measured nearthe Earth.We suggest that the heliospheric magnetic fields significantly affect the propagating ejecta. Sometimes, the ejecta may even rotate so that its axis locally aligns itself with the heliospheric current sheet.