Does spacecraft trajectory strongly affect detection of magnetic clouds?

Démoulin, P.; Dasso, S.; Janvier, Miho

doi:10.1051/0004-6361/201220535

Cited by 31 publications

(44 citation statements)

References 79 publications

(134 reference statements)

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“…The flux rope fitting is also impacted by various errors: magnetic field fluctuations inside the MC [Janoo et al, 1998], incorrect boundary selection, or noncircular MC cross section [Savani et al, 2011a[Savani et al, , 2011b. Also, when the impact parameter is high, the MC structure is not clearly identifiable as a cylindrical structure [e.g., Riley et al, 2004;Démoulin et al, 2013;Savani et al, 2013].…”

Section: 1002/2014ja020628mentioning

confidence: 99%

Statistical study of magnetic cloud erosion by magnetic reconnection

et al. 2015

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Several recent studies suggest that magnetic reconnection is able to erode substantial amounts of the outer magnetic flux of interplanetary magnetic clouds (MCs) as they propagate in the heliosphere. We quantify and provide a broader context to this process, starting from 263 tabulated interplanetary coronal mass ejections, including MCs, observed over a time period covering 17 years and at a distance of 1 AU from the Sun with Wind (1995Wind ( -2008 and the two STEREO (2009STEREO ( -2012 spacecraft. Based on several quality factors, including careful determination of the MC boundaries and main magnetic flux rope axes, an analysis of the azimuthal flux imbalance expected from erosion by magnetic reconnection was performed on a subset of 50 MCs. The results suggest that MCs may be eroded at the front or at rear and in similar proportions, with a significant average erosion of about 40% of the total azimuthal magnetic flux. We also searched for in situ signatures of magnetic reconnection causing erosion at the front and rear boundaries of these MCs. Nearly~30% of the selected MC boundaries show reconnection signatures. Given that observations were acquired only at 1 AU and that MCs are large-scale structures, this finding is also consistent with the idea that erosion is a common process. Finally, we studied potential correlations between the amount of eroded azimuthal magnetic flux and various parameters such as local magnetic shear, Alfvén speed, and leading and trailing ambient solar wind speeds. However, no significant correlations were found, suggesting that the locally observed parameters at 1 AU are not likely to be representative of the conditions that prevailed during the erosion which occurred during propagation from the Sun to 1 AU. Future heliospheric missions, and in particular Solar Orbiter or Solar Probe Plus, will be fully geared to answer such questions.

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Section: 1002/2014ja020628mentioning

confidence: 99%

Statistical study of magnetic cloud erosion by magnetic reconnection

et al. 2015

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“…The radial FR extension is deduced from Janvier et al (2014b). The FR cross section is elliptic with an aspect ratio of 2 as estimated by Démoulin et al (2013). The FR front is set at 1 AU, with the axis and shock shapes rescaled by their apex distances (0.87 and 1.1 AU respectively).…”

Section: Quantitative Generic Icme Structurementioning

confidence: 99%

Quantitative model for the generic 3D shape of ICMEs at 1 AU

Démoulin

Janvier

Masías-Meza

et al. 2016

A&A

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Context. Interplanetary imagers provide 2D projected views of the densest plasma parts of interplanetary coronal mass ejections (ICMEs) while in situ measurements provide magnetic field and plasma parameter measurements along the spacecraft trajectory, so along a 1D cut. As such, the data only give a partial view of their 3D structures. Aims. By studying a large number of ICMEs, crossed at different distances from their apex, we develop statistical methods to obtain a quantitative generic 3D shape of ICMEs. Methods. In a first approach we theoretically obtain the expected statistical distribution of the shock-normal orientation from assuming simple models of 3D shock shapes, including distorted profiles, and compare their compatibility with observed distributions. In a second approach we use the shock normal and the flux rope axis orientations, as well as the impact parameter, to provide statistical information across the spacecraft trajectory. Results. The study of different 3D shock models shows that the observations are compatible with a shock symmetric around the Sunapex line as well as with an asymmetry up to an aspect ratio around 3. Moreover, flat or dipped shock surfaces near their apex can only be rare cases. Next, the sheath thickness and the ICME velocity have no global trend along the ICME front. Finally, regrouping all these new results and the ones of our previous articles, we provide a quantitative ICME generic 3D shape, including the global shape of the shock, the sheath and the flux rope.Conclusions. The obtained quantitative generic ICME shape will have implications for several aims. For example, it constrains the output of typical ICME numerical simulations. It is also a base to develop deeper studies of the transport of high energy solar and cosmic particles during an ICME propagation, as well as for modeling and forecasting space weather conditions near Earth.

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“…The slope of the line, or simply slope of P obs (|λ|), is directly linked to the mean of the distribution |λ| (see Eq. (15) and related text in Démoulin et al 2013). Since the statistical fluctuations of the mean value of |λ| are on the order of |λ| √ N, where N is the number of MCs in the distribution, this fitting procedure allows us to split the MC data set in subsets while still keeping relatively low statistical fluctuations on the slope (see Fig.…”

Section: Distributions Of the Axis Orientationmentioning

confidence: 99%

Global axis shape of magnetic clouds deduced from the distribution of their local axis orientation

Janvier

Démoulin

Dasso

2013

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Context. Coronal mass ejections (CMEs) are routinely tracked with imagers in the interplanetary space, while magnetic clouds (MCs) properties are measured locally by spacecraft. However, both imager and in situ data do not provide any direct estimation of the general flux rope properties. Aims. The main aim of this study is to constrain the global shape of the flux rope axis from local measurements and to compare the results from in-situ data with imager observations. Methods. We performed a statistical analysis of the set of MCs observed by WIND spacecraft over 15 years in the vicinity of Earth. We analyzed the correlation between different MC parameters and studied the statistical distributions of the angles defining the local axis orientation. With the hypothesis of having a sample of MCs with a uniform distribution of spacecraft crossing along their axis, we show that a mean axis shape can be derived from the distribution of the axis orientation. As a complement, while heliospheric imagers do not typically observe MCs but only their sheath region, we analyze one event where the flux rope axis can be estimated from the STEREO imagers.Results. From the analysis of a set of theoretical models, we show that the distribution of the local axis orientation is strongly affected by the overall axis shape. Next, we derive the mean axis shape from the integration of the observed orientation distribution. This shape is robust because it is mostly determined from the overall shape of the distribution. Moreover, we find no dependence on the flux rope inclination on the ecliptic. Finally, the derived shape is fully consistent with the one derived from heliospheric imager observations of the June 2008 event. Conclusions. We have derived a mean shape of MC axis that only depends on one free parameter, the angular separation of the legs (as viewed from the Sun). This mean shape can be used in various contexts, such as studies of high-energy particles or space weather forecasts.

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Does spacecraft trajectory strongly affect detection of magnetic clouds?

Cited by 31 publications

References 79 publications

Statistical study of magnetic cloud erosion by magnetic reconnection

Statistical study of magnetic cloud erosion by magnetic reconnection

Quantitative model for the generic 3D shape of ICMEs at 1 AU

Global axis shape of magnetic clouds deduced from the distribution of their local axis orientation

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