Earth Planets Space, Vol. 61 (No. 5), pp. 589-594, 2009LETTER
Katsuhide Marubashi1, Suk-Kyung Sung1, Kyung-Suk Cho1, and Ronald P. Lepping2
1Space Science Division, Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea
2Space Weather Laboratory, NASA-Goddard Space Flight Center, Greenbelt, MD 20771, USA
(Received December 14, 2007; Revised April 17, 2008; Accepted April 18, 2008; Online published May 29, 2009)
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.
Key words: Interplanetary magnetic clouds, magnetic field structures, solar origins, geometrical relationships.