A comparison of the formation and evolution of magnetic flux ropes in solar coronal mass ejections and magnetotail plasmoids

Linton, M. G.; Moldwin, M. B.

doi:10.1029/2008ja013660

Cited by 39 publications

(26 citation statements)

References 159 publications

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“…Alternatively, simulations of single reconnection events in current sheets with guide fields have shown that the reconnected fields can sweep up unreconnected guide fields, creating a field rotation looking like a flux rope twist [Linton and Moldwin, 2009]. Lacking the high twist of flux ropes, the field line lengths in such cases would probably be much shorter than expected for flux ropes and more in accord with our results of a lack of clear difference between interior and exterior field line lengths of MCs.…”

Section: Implications For the Flux Rope Interpretationsupporting

confidence: 80%

Solar energetic electron probes of magnetic cloud field line lengths

2011

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[1] Magnetic clouds (MCs) are large interplanetary coronal mass ejections of enhanced and low-variance fields with rotations indicative of magnetic flux ropes originally connected to the Sun. The MC flux rope models require field lines with larger pitch angles and longer lengths with increasing distance from the MC axis. While the models can provide good fits to the in situ solar wind observations, there have not been definitive observational tests of the global magnetic field geometry, particularly for the field line lengths. However, impulsive solar energetic (E > 10 keV) electron events occasionally occur within an MC, and the electron onsets can be used to infer Le, the magnetic field line lengths traveled by the electrons from the Sun to the points in the MC where the electron onsets occur. We selected 8 MCs in and near which 30 solar electron events were observed by the 3DP instrument on the Wind spacecraft. We compared the corresponding Le values with calculated model field line lengths to test two MC models. Some limitations on the technique are imposed by variations of the models and uncertainly about MC boundary locations. We found generally poor correlations between the computed electron path lengths and the model field line lengths. Only one value of Le inside an MC, that of 18 October 1995, exceeded 3.2 AU, indicating an absence of the long path lengths expected in the highly wound outer regions of MC models. We briefly consider the implications for MC models.

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Section: Implications For the Flux Rope Interpretationsupporting

confidence: 80%

Solar energetic electron probes of magnetic cloud field line lengths

2011

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“…In such a scenario, the small FRs would result from multiple reconnections during the development of the tearing instability in the HCS. This process is similar to that advocated for the FR formation above streamers and for the ones observed in the Earth's magnetotail (Linton and Moldwin, 2009 and references therein). However, similarly as for simulations for helmet streamers, the thickness of the HCS is too small to clearly explain the formation of structures as large as 0.05 AU: the HCS is ≈ 10 4 km at 1 AU, so less than 10 −4 AU (e.g.…”

Section: What Origins For the Small Flux Ropes?mentioning

confidence: 53%

Are There Different Populations of Flux Ropes in the Solar Wind?

2014

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Flux ropes are twisted magnetic structures, which can be detected by in-situ measurements in the solar wind. However, different properties of detected flux ropes suggest different types of flux-rope population. As such, are there different populations of flux ropes? The answer is positive, and is the result of the analysis of four lists of flux ropes, including magnetic clouds (MCs), observed at 1 AU. The in-situ data for the four lists have been fitted with the same cylindrical force-free model, which provides an estimation of the local flux-rope parameters such as its radius and orientation. Since the flux-rope distributions have a large dynamic range, we go beyond a simple histogram analysis by developing a partition technique that uniformly distributes the statistical fluctuations over the radius range. By doing so, we find that small flux ropes with radius R < 0.1 AU have a steep power-law distribution in contrast to the larger flux ropes (identified as MCs), which have a Gaussian-like distribution. Next, from four CME catalogs, we estimate the expected flux-rope frequency per year at 1 AU. We find that the predicted numbers are similar to the frequencies of MCs observed in-situ. However, we also find that small flux ropes are at least ten times too abundant to correspond to CMEs, even to narrow ones. Investigating the different possible scenarios for the origin of those small flux ropes, we conclude that these twisted structures can be formed by blowout jets in the low corona or in coronal streamers.

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“…This has led to much new research on flux-rope CMEs, and it is now generally accepted that CMEs are expanding flux ropes. [88][89][90][91][92][93] In their simplest form, flux ropes are self-organized plasma pinches (Sec. III D), and the appellation refers to the braided (twisted) "ropes" of helical magnetic field "lines" characteristic of such structures.…”

Section: -5mentioning

confidence: 99%

Physics of erupting solar flux ropes: Coronal mass ejections (CMEs)—Recent advances in theory and observation

Chen

2017

Physics of Plasmas

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Solar eruptions, observed as flares and coronal mass ejections (CMEs), are the most energetic visible plasma phenomena in the solar system. CMEs are the central component of solar eruptions and are detected as coherent magnetized plasma structures expanding in the solar wind (SW). If they reach the Earth, their magnetic fields can drive strong disturbances in the ionosphere, causing deleterious effects on terrestrial technological systems. The scientific and practical importance of CMEs has led to numerous satellite missions observing the Sun and SW. This has culminated in the ability to continuously observe CMEs expanding from the Sun to 1 AU, where the magnetic fields and plasma parameters of the evolved structures ("ejecta") can be measured in situ. Until recently, the physical mechanisms responsible for eruptions were major unanswered questions in solar and by extension stellar physics. New observations of CME dynamics and associated eruptive phenomena are now providing more stringent constraints on models, and quantitative theory-data comparisons are helping to establish the correct mechanism of solar eruptions, particularly the driving force of CMEs and the evolution of their magnetic fields in three dimensions. Recent work has demonstrated that theoretical results can simultaneously replicate the observed CME position-time data, temporal profiles of associated solar flare soft X-ray emissions, and the magnetic field and plasma parameters of CME ejecta measured at 1 AU. Thus, a new theoretical framework with testable predictions is emerging to model eruptions and the coupling of CME ejecta to geomagnetic disturbances. The key physics in CME dynamics is the Lorentz hoop force acting on toroidal "flux ropes," scalable from tokamaks and similar laboratory plasma structures. The present paper reviews the latest advances in observational and theoretical understanding of CMEs with the emphasis on quantitative comparisons of theory and observation. Published by AIP Publishing.

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A comparison of the formation and evolution of magnetic flux ropes in solar coronal mass ejections and magnetotail plasmoids

Cited by 39 publications

References 159 publications

Solar energetic electron probes of magnetic cloud field line lengths

Solar energetic electron probes of magnetic cloud field line lengths

Are There Different Populations of Flux Ropes in the Solar Wind?

Physics of erupting solar flux ropes: Coronal mass ejections (CMEs)—Recent advances in theory and observation

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