Eruptions of two flux ropes observed by SDO and STEREO

Li, L. P.; Zhang, J.

doi:10.1051/0004-6361/201221005

Cited by 52 publications

(41 citation statements)

References 24 publications

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“…Only in a small percentage of cases can we exclude the presence of a flux rope. Moreover, additional studies, directly involving AIA, have shown that flux ropes are formed and ejected during a CME (Chen 2011;Li & Zhang 2013). From a theoretical point of view, a number of studies have shown that the ejection of a flux rope is sufficient to reproduce the main observed features of CMEs: Török & Kliem (2007), Fan (2010), and Aulanier et al (2010) explain the ejection with the occurrence of a Torus instability; Fan (2009) and Archontis et al (2009) with a flux emergence event; Savcheva et al (2012) with the rotation of footpoints; Amari et al (2003) with shearing and flux cancellation, while Amari et al (2011) use convergence of foot points; finally Roussev et al (2012) consider a global reorganisation of the solar corona.…”

Section: Introductionmentioning

confidence: 99%

Simulating AIA observations of a flux rope ejection

Pagano

Mackay

Poedts

2014

A&A

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Context. Coronal mass ejections (CMEs) are the most violent phenomena observed on the Sun. Currently, extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. In particular, observations now show the ejection of magnetic flux ropes from the solar corona and how they evolve into CMEs. While this is the case, these observations are difficult to interpret in terms of basic physical mechanisms and quantities. To fully understand CMEs we need to compare equivalent quantities derived from both observations and theoretical models. This will aid in bridging the gap between observations and models. Aims. To this end, we aim to produce synthesised AIA observations from simulations of a flux rope ejection. To carry this out we include the role of thermal conduction and radiative losses, both of which are important for determining the temperature distribution of the solar corona during a CME. Methods. We perform a simulation where a flux rope is ejected from the solar corona. From the density and temperature of the plasma in the simulation we synthesise AIA observations. The emission is then integrated along the line of sight using the instrumental response function of AIA. Results. We sythesise observations of AIA in the channels at 304 Å, 171 Å, 335 Å, and 94 Å. The synthesised observations show a number of features similar to actual observations and in particular reproduce the general development of CMEs in the low corona as observed by AIA. In particular we reproduce an erupting and expanding arcade in the 304 Å and 171 Å channels with a high density core. Conclusions. The ejection of a flux rope reproduces many of the features found in the AIA observations. This work is therefore a step forward in bridging the gap between observations and models, and can lead to more direct interpretations of EUV observations in terms of flux rope ejections. We plan to improve the model in future studies in order to perform a more quantitative comparison.

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Section: Introductionmentioning

confidence: 99%

Simulating AIA observations of a flux rope ejection

Pagano

Mackay

Poedts

2014

A&A

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“…Recently, Zhang et al (2012) and Cheng et al (2013a) reported the existence of EUV hot channels that appeared in the high temperature passbands of the Atmospheric Imaging Assembly (AIA) telescope (Lemen et al 2012) tens of minutes before the eruption. Once the impulsive acceleration phase starts, the hot channel erupts upward and develops into a semicircular shape (also see Liu et al 2010a;Patsourakos et al 2013;Li & Zhang 2013a). Detailed morphology and kinematic analyses suggest that the hot channel is most likely to be the MFR and plays a critical role in forming and accelerating the CME in the inner corona (Cheng et al 2013a(Cheng et al , 2013bPatsourakos & Vourlidas 2012).…”

Section: Introductionmentioning

confidence: 99%

Tracking the Evolution of a Coherent Magnetic Flux Rope Continuously From the Inner to the Outer Corona

Cheng

Ding

Guo

et al. 2013

ApJ

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The magnetic flux rope (MFR) is believed to be the underlying magnetic structure of coronal mass ejections (CMEs). However, it remains unclear how an MFR evolves into and forms the multi-component structure of a CME. In this paper, we perform a comprehensive study of an extreme-ultraviolet (EUV) MFR eruption on 2013 May 22 by tracking its morphological evolution, studying its kinematics, and quantifying its thermal property. As EUV brightenings begin, the MFR starts to rise slowly and shows helical threads winding around an axis. Meanwhile, cool filamentary materials descend spirally down to the chromosphere. These features provide direct observational evidence of intrinsically helical structure of the MFR. Through detailed kinematical analysis, we find that the MFR evolution has two distinct phases: a slow rise phase and an impulsive acceleration phase. We attribute the first phase to the magnetic reconnection within the quasi-separatrix layers surrounding the MFR, and the much more energetic second phase to the fast magnetic reconnection underneath the MFR. We suggest that the transition between these two phases is caused by the torus instability. Moreover, we identify that the MFR evolves smoothly into the outer corona and appears as a coherent structure within the white-light CME volume. The MFR in the outer corona was enveloped by bright fronts that originated from plasma pile-up in front of the expanding MFR. The fronts are also associated with the preceding sheath region followed by the outmost MFR-driven shock.

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“…Often magnetic flux ropes in the low corona are considered the main progenitors of CMEs, where an initial period of stability of the flux rope is followed by a fast and sudden ejection outwards into interplanetary space. This scenario is supported by a number of observations (Howard & DeForest, 2014;Chintzoglou et al, 2015;Cheng et al, 2011;Li & Zhang, 2013). Some models explain the flux rope formation and the subsequent ejection with photospheric flows (Mackay & van Ballegooijen, 2006a;Xia et al, 2014), others focus on magnetic flux emergence from underneath the photosphere (Archontis & Hood, 2012), and finally others rely on the onset of MHD instabilities (Török & Kliem, 2005;Zuccarello et al, 2015).…”

Section: Introductionmentioning

confidence: 74%

A new technique for observationally derived boundary conditions for space weather

Pagano

Mackay

Yeates

2018

J. Space Weather Space Clim.

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-Context. In recent years, space weather research has focused on developing modelling techniques to predict the arrival time and properties of coronal mass ejections (CMEs) at the Earth. The aim of this paper is to propose a new modelling technique suitable for the next generation of Space Weather predictive tools that is both efficient and accurate. The aim of the new approach is to provide interplanetary space weather forecasting models with accurate time dependent boundary conditions of erupting magnetic flux ropes in the upper solar corona. Methods. To produce boundary conditions, we couple two different modelling techniques, MHD simulations and a quasi-static non-potential evolution model. Both are applied on a spatial domain that covers the entire solar surface, although they extend over a different radial distance. The non-potential model uses a time series of observed synoptic magnetograms to drive the non-potential quasi-static evolution of the coronal magnetic field. This allows us to follow the formation and loss of equilibrium of magnetic flux ropes. Following this a MHD simulation captures the dynamic evolution of the erupting flux rope, when it is ejected into interplanetary space. Results.The present paper focuses on the MHD simulations that follow the ejection of magnetic flux ropes to 4 R ⊙ . We first propose a technique for specifying the pre-eruptive plasma properties in the corona. Next, time dependent MHD simulations describe the ejection of two magnetic flux ropes, that produce time dependent boundary conditions for the magnetic field and plasma at 4 R ⊙ that in future may be applied to interplanetary space weather prediction models. Conclusions. In the present paper, we show that the dual use of quasi-static non-potential magnetic field simulations and full time dependent MHD simulations can produce realistic inhomogeneous boundary conditions for space weather forecasting tools. Before a fully operational model can be produced there are a number of technical and scientific challenges that still need to be addressed. Nevertheless, we illustrate that coupling quasi-static and MHD simulations in this way can significantly reduce the computational time required to produce realistic space weather boundary conditions.

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Eruptions of two flux ropes observed by SDO and STEREO

Cited by 52 publications

References 24 publications

Simulating AIA observations of a flux rope ejection

Simulating AIA observations of a flux rope ejection

Tracking the Evolution of a Coherent Magnetic Flux Rope Continuously From the Inner to the Outer Corona

A new technique for observationally derived boundary conditions for space weather

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