Superposed epoch study of ICME sub-structures near Earth and their effects on Galactic cosmic rays

Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Rodriguez, L.; Janvier, Miho

doi:10.1051/0004-6361/201628571

Cited by 67 publications

(132 citation statements)

References 48 publications

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“…Masías-Meza et al 2016). Two physical mechanisms are typically thought to explain the depletion of cosmic ray fluxes (which occur in two steps): the deflection of particles by the more intense ICME magnetic field and by the turbulence properties at the ICME shock (the so-called diffusive barrier, e.g.…”

Section: Resultsmentioning

confidence: 99%

“…The sheath has typically a magnetic field strength comparable, or even larger, than the following MC (e.g. Zurbuchen & Richardson 2006;Masías-Meza et al 2016). In the sheath, the magnetic field rapidly changes its orientation (this is due to different solar wind structures pressed together) and the proton temperature is typically much higher than in the solar wind and even more than in MCs (due to a strong compression and an enhanced heating).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

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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“…The spacecraft provides a continuous coverage of SW parameters. Similarly to Masías‐Meza et al (), we use the 1‐s time cadence IMF and 64‐s time cadence plasma measurements from two of the instruments aboard the spacecraft (MAG and SWEPAM experiments, see McComas et al, ; Smith et al, ). The data from ACE are directly available online at http://www.srl.caltech.edu/ACE/ASC/level2/.…”

Section: Description Of the Data Setsmentioning

confidence: 99%

“…The Venus Express ICME catalog is provided by Good and Forsyth (). The ACE ICME catalog used here come from Masías‐Meza et al (). All superposed epoch data from this paper have been made available online at https://figshare.com/s/3e0394e629fbed907152.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Generic Magnetic Field Intensity Profiles of Interplanetary Coronal Mass Ejections at Mercury, Venus, and Earth From Superposed Epoch Analyses

et al. 2019

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We study interplanetary coronal mass ejections (ICMEs) measured by probes at different heliocentric distances (0.3–1 AU) to investigate the propagation of ICMEs in the inner heliosphere and determine how the generic features of ICMEs change with heliospheric distance. Using data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER), Venus Express and ACE spacecraft, we analyze with the superposed epoch technique the profiles of ICME substructures, namely, the sheath and the magnetic ejecta. We determine that the median magnetic field magnitude in the sheath correlates well with ICME speeds at 1 AU, and we use this proxy to order the ICMEs at all spacecraft. We then investigate the typical ICME profiles for three categories equivalent to slow, intermediate, and fast ICMEs. Contrary to fast ICMEs, slow ICMEs have a weaker solar wind field at the front and a more symmetric magnetic field profile. We find the asymmetry to be less pronounced at Earth than at Mercury, indicating a relaxation taking place as ICMEs propagate. We also find that the magnetic field intensities in the wake region of the ICMEs do not go back to the pre‐ICME solar wind intensities, suggesting that the effects of ICMEs on the ambient solar wind last longer than the duration of the transient event. Such results provide an indication of physical processes that need to be reproduced by numerical simulations of ICME propagation. The samples studied here will be greatly improved by future missions dedicated to the exploration of the inner heliosphere, such as Parker Solar Probe and Solar Orbiter.

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“…It can be noted that the size of the FD region (interval 45–54 hr) is smaller than the MC transverse dimension. However, in real events, FDs are observed throughout or even longer than the entire passage of MCs (Belov et al, ; Masías‐Meza et al, ). In our model, there is no FD during 41–45 and 55–61 hr because: (1) There are CRs that have recently entered the MC and have not experienced its effect.…”

Section: Calculation Results and Discussionmentioning

confidence: 99%

Image of Forbush Decrease in a Magnetic Cloud by Three Moments of Cosmic Ray Distribution Function

Petukhova

Petukhov

2019

JGR Space Physics

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The time dynamics of the cosmic ray distribution function in a magnetic cloud is calculated. The magnetic cloud has the form of a torus segment with the force‐free magnetic field structure at the initial moment. The subsequent propagation of the magnetic cloud in interplanetary space is determined by inertial description. The magnetic field is determined by the frozen‐in condition. When calculating the particle distribution function, the electromagnetic field of the magnetic cloud is taken into account, with the scattering of particles not being taken into account. Relations between the particle distribution function and its three moments (particle density and unidirectional and bidirectional anisotropies) are derived. It is established that cosmic ray losses at the regions connecting the magnetic cloud with the Sun determine the amplitude of the second step of Forbush decrease. The time dependence of the Forbush decrease characteristics on magnetic cloud type is determined. The calculation results of the particle density and unidirectional anisotropy generally correspond to measurements. The referred results show a prominent role of the magnetic field structure in the time dynamics of the Forbush decrease.

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Superposed epoch study of ICME sub-structures near Earth and their effects on Galactic cosmic rays

Cited by 67 publications

References 48 publications

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

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

Generic Magnetic Field Intensity Profiles of Interplanetary Coronal Mass Ejections at Mercury, Venus, and Earth From Superposed Epoch Analyses

Image of Forbush Decrease in a Magnetic Cloud by Three Moments of Cosmic Ray Distribution Function

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