Characterizing and predicting the magnetic environment leading to solar eruptions

Amari, T.; Canou, A.; Aly, J. J.

doi:10.1038/nature13815

Cited by 159 publications

(136 citation statements)

References 47 publications

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“…The latter is referred to as "torus instability." The role of the torus instability in flux rope eruptions has also been investigated in less-idealized configurations such as line-tied T&D (Titov & Démoulin 1999) flux ropes, dynamically formed flux ropes as well as MHD relaxations of nonlinear force-free equilibria of solar active regions (Török & Kliem 2005Fan & Gibson 2007;Isenberg & Forbes 2007;Aulanier et al 2010;Fan 2010;Kliem et al 2013;Amari et al 2014;Inoue et al 2015). These numerical MHD simulations suggest values of the critical decay index in the range = -n 1.5 1.9 crit .…”

Section: Introductionmentioning

confidence: 99%

The Apparent Critical Decay Index at the Onset of Solar Prominence Eruptions

Zuccarello

Aulanier

Gilchrist

2016

ApJL

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A magnetic flux rope (MFR) embedded in a line-tied external magnetic field that decreases with height asz n is unstable to perturbations if the decay index of the field n is larger than a critical value. The onset of this instability, called torus instability, is one of the main mechanisms that can initiate coronal mass ejections. Since flux ropes often possess magnetic dips that can support prominence plasma, this is also a valuable mechanism to trigger prominence eruptions. Magnetohydrodynamic (MHD) simulations of the formation and/or emergence of MFRs suggest a critical value for the onset of the instability in the range [1.4−2]. However, detailed observations of prominences suggest a value in the range [0.9−1.1]. In this Letter, by using a set of MHD simulations, we show why the large discrepancy between models and observations is only apparent. Our simulations indeed show that the critical decay index at the onset of the eruption is =  n 1.4 0.1 when computed at the apex of the flux rope axis, while it is =  n 1.1 0.1 when it is computed at the altitude of the topmost part of the distribution of magnetic dips. The discrepancy only arises because weakly twisted curved flux ropes do not have dips up to the altitude of their axis.

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Section: Introductionmentioning

confidence: 99%

The Apparent Critical Decay Index at the Onset of Solar Prominence Eruptions

Zuccarello

Aulanier

Gilchrist

2016

ApJL

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“…Many models use observed magnetograms as boundary condition for the magnetic field at the lower boundary, and recently observed surface flows have been included as well (Jiang et al 2016). Some simulations restrict the calculation to the evolution in the corona (e.g., Zuccarello et al 2012b;Amari et al 2014;Fan 2016), while others model the propagation of the ejecta to 1 AU but do not include the coronal evolution. Instead, the latter models start the simulation in the inner heliosphere (typically at around 20-30 R ) and use for the initial ICME some idealized model whose parameters are chosen guided by coronagraph observations (e.g., Shiota and Kataoka 2016).…”

Section: Modeling Cmes From Sun To Earth: the Bastille Day Eventmentioning

confidence: 99%

The Physical Processes of CME/ICME Evolution

et al. 2017

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As observed in Thomson-scattered white light, coronal mass ejections (CMEs) are manifest as large-scale expulsions of plasma magnetically driven from the corona in the most energetic eruptions from the Sun. It remains a tantalizing mystery as to how these erupting magnetic fields evolve to form the complex structures we observe in the solar wind at Earth. Here, we strive to provide a fresh perspective on the post-eruption and interplanetary evolution of CMEs, focusing on the physical processes that define the many complex interactions of the ejected plasma with its surroundings as it departs the corona and propagates through the heliosphere. We summarize the ways CMEs and their interplanetary CMEs (ICMEs) are rotated, reconfigured, deformed, deflected, decelerated and disguised during their journey through the solar wind. This study then leads to consideration of how structures originating in coronal eruptions can be connected to their far removed interplanetary counterparts. Given that ICMEs are the drivers of most geomagnetic storms (and the sole driver of extreme storms), this work provides a guide to the processes that must be considered in making space weather forecasts from remote observations of the corona.

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“…Most of them are modeled in Cartesian coordinates, although some models are reconstructed in spherical geometry (Su et al 2009;Tadesse et al 2011;Guo et al 2012) or with tetrahedral meshes (Amari et al 2014b). In particular, Amari et al (2014a) has developed another code to fulfill the need for reconstructions on the scale of local active regions within a global extrapolation, using an iterative GradRubin scheme adapted to spherical coordinates.…”

Section: Introductionmentioning

confidence: 99%

Magneto-Frictional Modeling of Coronal Nonlinear Force-Free Fields. Ii. Application to Observations

Guo

Xia

Keppens

2016

ApJ

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A magneto-frictional module has been implemented and tested in the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC) in the first paper of this series. Here, we apply the magneto-frictional method to observations to demonstrate its applicability in both Cartesian and spherical coordinates, and in uniform and block-adaptive octree grids. We first reconstruct a nonlinear force-free field (NLFFF) on a uniform grid of 180 3 cells in Cartesian coordinates, with boundary conditions provided by the vector magnetic field observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) at 06:00 UT on 2010 November 11 in active region NOAA 11123. The reconstructed NLFFF successfully reproduces the sheared and twisted field lines and magnetic null points. Next, we adopt a three-level block-adaptive grid to model the same active region with a higher spatial resolution on the bottom boundary and a coarser treatment of regions higher up. The force-free and divergence-free metrics obtained are comparable to the run with a uniform grid, and the reconstructed field topology is also very similar. Finally, a group of active regions, including NOAA 11401, 11402, 11405, and 11407, observed at 03:00 UT on 2012 January 23 by SDO/HMI is modeled with a five-level block-adaptive grid in spherical coordinates, where we reach a local resolution of  0 . 06 pixel −1 in an area of 790 Mm×604 Mm. Local high spatial resolution and a large field of view in NLFFF modeling can be achieved simultaneously in parallel and block-adaptive magneto-frictional relaxations.

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Characterizing and predicting the magnetic environment leading to solar eruptions

Cited by 159 publications

References 47 publications

The Apparent Critical Decay Index at the Onset of Solar Prominence Eruptions

The Apparent Critical Decay Index at the Onset of Solar Prominence Eruptions

The Physical Processes of CME/ICME Evolution

Magneto-Frictional Modeling of Coronal Nonlinear Force-Free Fields. Ii. Application to Observations

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