Multispacecraft observation of magnetic cloud erosion by magnetic reconnection during propagation

Ruffenach, A.; Lavraud, B.; Owens, M. J.; Sauvaud, J. A.; Savani, N. P.; Rouillard, A. P.; Démoulin, P.; Foullon, Claire; Opitz, A.; Fedorov, A.; Jacquey, C.; Génot, Vincent; Louarn, P.; Luhmann, J. G.; Russell, C. T.; Farrugia, C. J.; Galvin, A. B.

doi:10.1029/2012ja017624

Cited by 166 publications

(185 citation statements)

References 112 publications

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“…Typically, their magnetic field is too weak and/or irregular or without much rotation. Some of these ejecta can be further classified into sub-categories, for example, "magnetic cloud-like" (Zhang et al, 2007) or magnetic flux rope (Rouillard, 2011). It has been recently proposed that some of these events are actually MCs whose legs passed through the observing spacecraft (Marubashi and Lepping, 2007), which has been confirmed with STEREO observations (Möstl et al, 2010).…”

Section: Introductionmentioning

confidence: 67%

Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass Ejections

et al. 2013

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This study aims to provide a reference to different magnetic field models and reconstruction methods for interplanetary coronal mass ejections (ICMEs). In order to understand the differences in the outputs of those models and codes, we analyze 59 events from the Coordinated Data Analysis Workshop (CDAW) list, using four different magnetic field models and reconstruction techniques; force-free fitting (Goldstein, 1983; Burlaga, 1988;Lepping, Burlaga, and Jones, 1990), magnetostatic reconstruction using a numerical solution to the Grad-Shafranov equation (Hu and Sonnerup, 2001), fitting to a self-similarly expanding cylindrical configuration (Marubashi and Lepping, 2007) and elliptical, non-force free fitting (Hidalgo, 2003). The resulting parameters of the reconstructions for the 59 events are compared statistically, as well as in selected case studies. The ability of a method to fit or reconstruct an event is found to vary greatly: the Grad-Shafranov reconstruction is successful for most magnetic clouds (MCs) but for less than 10% of the non-MC ICMEs; the other three Al-Haddad et al methods provide a successful fit for more than 65% of all events. The differences between the reconstruction and fitting methods are discussed, and suggestions are proposed as to how to reduce them. We find that the magnitude of the axial field is relatively consistent across models but not the orientation of the axis of the ejecta. We also find that there are a few cases for which different signs of the magnetic helicity are found for the same event when we do not fix the boundaries, illustrating that this simplest of parameters is not necessarily always well constrained by fitting and reconstruction models. Finally, we look at three unique cases in depth to provide a comprehensive idea of the different aspects of how the fitting and reconstruction codes work.

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Section: Introductionmentioning

confidence: 67%

Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass Ejections

et al. 2013

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“…The fraction of eroded azimuthal flux is relatively high in some MCs, for example, about 60% for the MC observed by Wind on 18 Oct. 1995 (Dasso et al 2006), while it is 44% and 49% of the initial azimuthal magnetic flux for the same MC observed on 20 Nov. 2007 by ACE and STEREO A respectively (Ruffenach et al 2012). Then, it is plausible that some flux ropes are even more eroded and then remain undetected at 1 AU, while the spacecraft is crossing close to the shock apex.…”

Section: What Is the Nature Of Non-detected Icme Shocks?mentioning

confidence: 99%

Mean shape of interplanetary shocks deduced from in situ observations and its relation with interplanetary CMEs

Janvier

Démoulin

Dasso

2014

A&A

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Context. Shocks are frequently detected by spacecraft in the interplanetary space. However, the in situ data of a shock do not provide direct information on its overall properties even when a following interplanetary coronal mass ejection (ICME) is detected. Aims. The main aim of this study is to constrain the general shape of ICME shocks with a statistical study of shock orientations. Methods. We first associated a set of shocks detected near Earth over 10 years with a sample of ICMEs over the same period. We then analyzed the correlations between shock and ICME parameters and studied the statistical distributions of the local shock normal orientation. Supposing that shocks are uniformly detected all over their surface projected on the 1 AU sphere, we compared the shock normal distribution with synthetic distributions derived from an analytical shock shape model. Inversely, we derived a direct method to compute the typical general shape of ICME shocks by integrating observed distributions of the shock normal. Results. We found very similar properties between shocks with and without an in situ detected ICME, so that most of the shocks detected at 1 AU are ICME-driven even when no ICME is detected. The statistical orientation of shock normals is compatible with a mean shape having a rotation symmetry around the Sun-apex line. The analytically modeled shape captures the main characteristics of the observed shock normal distribution. Next, by directly integrating the observed distribution, we derived the mean shock shape, which is found to be comparable for shocks with and without a detected ICME and weakly affected by the limited statistics of the observed distribution. We finally found a close correspondence between this statistical result and the leading edge of the ICME sheath that is observed with STEREO imagers. Conclusions. We have derived a mean shock shape that only depends on one free parameter. This mean shape can be used in various contexts, such as studies for high-energy particles or space weather forecasts.

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“…The strong correlation R(p) is also surprising. Still, we emphasize the study of V because R could be affected by the amount of reconnection achieved between the MC and the overtaken magnetic field as deduced by the presence of a back region in MCs (Dasso et al 2006Ruffenach et al 2012). …”

Section: Correlation Between MC Parametersmentioning

confidence: 99%

Does spacecraft trajectory strongly affect detection of magnetic clouds?

Démoulin

Dasso

Janvier

2013

A&A

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Context. Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). One property of MCs is the presence of a magnetic flux rope. Is the difference between ICMEs with and without MCs intrinsic or rather due to an observational bias? Aims. As the spacecraft has no relationship with the MC trajectory, the frequency distribution of MCs versus the spacecraft distance to the MCs' axis is expected to be approximately flat. However, Lepping & Wu (2010, Ann. Geophys., 28, 1539 confirmed that it is a strongly decreasing function of the estimated impact parameter. Is a flux rope more frequently undetected for larger impact parameter? Methods. In order to answer the questions above, we explore the parameter space of flux rope models, especially the aspect ratio, boundary shape, and current distribution. The proposed models are analyzed as MCs by fitting a circular linear force-free field to the magnetic field computed along simulated crossings. Results. We find that the distribution of the twist within the flux rope and the non-detection due to too low field rotation angle or magnitude only weakly affect the expected frequency distribution of MCs versus impact parameter. However, the estimated impact parameter is increasingly biased to lower values as the flux rope cross section is more elongated orthogonally to the crossing trajectory. The observed distribution of MCs is a natural consequence of a flux rope cross section flattened on average by a factor 2 to 3 depending on the magnetic twist profile. However, the faster MCs at 1 AU, with V > 550 km s −1 , present an almost uniform distribution of MCs vs. impact parameter, which is consistent with round-shaped flux ropes, in contrast with the slower ones. Conclusions. We conclude that the sampling of MCs at various distances from the axis does not significantly affect their detection. The large part of ICMEs without MCs could be due to a too strict criteria for MCs or to the fact that these ICMEs are encountered outside their flux rope or near the leg region, or they do not contain a flux rope.

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Multispacecraft observation of magnetic cloud erosion by magnetic reconnection during propagation

Cited by 166 publications

References 112 publications

Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass Ejections

Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass Ejections

Mean shape of interplanetary shocks deduced from in situ observations and its relation with interplanetary CMEs

Does spacecraft trajectory strongly affect detection of magnetic clouds?

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