Abstract
Abstract Our recent analysis of interplanetary magnetic clouds (MCs) showed that the orientations of MC axes determined by a model fitting with curvature of MCs taken into account (referred to as a torus model, hereafter) can be significantly different from those obtained from fittings with a straight cylinder model. Motivated by this finding, we re-examined geometrical relationships between magnetic field structures of MCs and their solar origins. This paper describes the results of the re-examination with special attention paid to two MC events, for which different orientations of MC axes were obtained from a torus model and a cylinder model. For both cases, it is shown that the torus models give the MC geometries of magnetic field structures in good agreement with those of coronal arcade structures which were formed in association with the launch of MCs along the magnetic field inversion lines. Summarizing the analysis results for 12 MCs investigated here, we conclude that: (1) the formation of coronal arcade structure is a good indication of MC formation; (2) MC geometries can be obtained that are consistent with the coronal arcades with respect to the axis orientation and the magnetic field structure including chirality, indicating that no significant direction changes occurred during the propagation of MCs through the interplanetary medium.
Highlights
The interplanetary magnetic cloud (MC) occupies the whole body or a significant part of a plasma cloud ejected into the solar wind in association with the coronal mass ejection (CME)
Most previous studies on this subject have shown that the orientations of MCs are roughly aligned with the inversion lines of photospheric longitudinal magnetic fields in the associated CME sites and that the chirality of MCs are of the same sign as the chirality of solar magnetic fields in the source regions (e.g., Marubashi, 1986, 1997; Bothmer and Schwenn, 1994; Bothmer and Rust, 1997; Yurchyshyn et al, 2001)
This finding impacts on our understanding the connection between MCs and CMEs and suggests that it may be possible to obtain a better agreement between the MC orientations and the solar magnetic inversion lines if the MC geometries are determined with a torus model
Summary
The interplanetary magnetic cloud (MC) occupies the whole body or a significant part of a plasma cloud ejected into the solar wind in association with the coronal mass ejection (CME). Most previous studies on this subject have shown that the orientations of MCs are roughly aligned with the inversion lines of photospheric longitudinal magnetic fields in the associated CME sites and that the chirality of MCs are of the same sign as the chirality of solar magnetic fields in the source regions (e.g., Marubashi, 1986, 1997; Bothmer and Schwenn, 1994; Bothmer and Rust, 1997; Yurchyshyn et al, 2001). Their comparison of the MC orientations determined from the torus and cylinder models revealed that there are such MC events for which observations can be as well explained by either of the models but that the obtained orientations are significantly different from each other This finding impacts on our understanding the connection between MCs and CMEs and suggests that it may be possible to obtain a better agreement between the MC orientations and the solar magnetic inversion lines if the MC geometries are determined with a torus model
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