Eruptivity Criteria for Two-Dimensional Magnetic Flux Ropes in the Solar Corona

Rice, Oliver E. K.; Yeates, Anthony R.

doi:10.3389/fspas.2022.849135

Cited by 5 publications

(6 citation statements)

References 40 publications

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“…Nindos & Andrews 2004;LaBonte et al 2007;Park et al 2010;Tziotziou et al 2012;Vemareddy 2019;Liokati et al 2022). Recently, in a 2D parametric numerical study, Rice & Yeates (2022) found that major eruptions were best predicted by thresholds in the ratios of rope current to magnetic energy of helicity. They noted that the helicity eruptivity index was negatively correlated with eruptions.…”

Section: Discussionmentioning

confidence: 99%

Comparison of magnetic energy and helicity in coronal jet simulations

Pariat

Wyper

Linan

2023

A&A

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Context.While free/non-potential magnetic energy is a necessary element of any active phenomenon in the solar corona, its role as a marker of the trigger of eruptive process remains elusive. Meanwhile, recent analysis of numerical simulations of solar active events have shown that quantities based on relative magnetic helicity could highlight the eruptive nature of solar magnetic systems. Aims. Based on the unique decomposition of the magnetic field into potential and non-potential components, magnetic energy and helicity can also both be uniquely decomposed into two quantities. Using two 3D magnetohydrodynamics parametric simulations of a configuration that can produce coronal jets, we compare the dynamics of the magnetic energies and of the relative magnetic helicities. Methods. Both simulations share the same initial set-up and line-tied bottom-boundary driving profile. However they differs by the duration of the forcing. In one simulation, analysed in Wyper et al. ( 2018), the system is driven sufficiently so that a point of no-return is passed, and that the system induces the generation of an helical jet. The generation of the jet is however markedly delayed after the end of the driving phase: a relatively long phase of lower-intensity reconnection takes place before the jet is eventually induced. In the other reference simulation, the system is driven during a shorter time, and no jet is produced. Results. As expected, we observe that the Jet producing simulation contains a higher value of non-potential energy and non-potential helicity compared to the non-eruptive system. Focussing on the phase between the end of the driving-phase and the jet generation, we note that magnetic energies remain relatively constant, while magnetic helicities have a noticeable evolution. During this post-driving phase, the ratio of the non-potential to total magnetic energy very slightly decreases while the helicity eruptivity index, that is the ratio of the non-potential helicity to the total relative magnetic helicity, significantly increases. The jet is generated when the system is at the highest value of this helicity eruptivity index. This proxy critically decreases during the jet generation phase. The free energy also decreases but does not present any peak when the jet is being generated. Conclusions. Our study further strengthens the importance of helicities, and in particular of the helicity eruptivity index, to understand the trigger of solar eruptive events.

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Section: Discussionmentioning

confidence: 99%

Comparison of magnetic energy and helicity in coronal jet simulations

Pariat

Wyper

Linan

2023

A&A

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“…As in our previous work (Rice & Yeates 2022), the cartesian simulations (both magnetofriction and MHD) are initialized with the lower boundary condition…”

Section: Initial Conditionsmentioning

confidence: 99%

“…We previously established (Rice & Yeates 2022) that no single diagnostic is a good predictor of eruptivity. This is also true in these new simulations, and so we instead focus on ratios between them (e.g.,…”

Section: Diagnostic Measuresmentioning

confidence: 99%

“…This paper builds on our previous work (Rice & Yeates 2022), in which we studied the formation and eruption of magnetic flux ropes using a translationally invariant (2.5D) cartesian magnetofrictional (MF) model. Here, we expand the study to include two further models: a second MF model in axisymmetric polar coordinates and a full magnetohydrodynamic (MHD) model in cartesian coordinates.…”

Section: Introductionmentioning

confidence: 99%

“…Our previous study on the eruptivity of flux ropes (Rice & Yeates 2022) sought a compromise between simple analytical models and full 3D MHD simulations, by using the MF model in a 2.5D cartesian domain. In the MF model, pioneered by Yang et al (1986), the fluid equations are disregarded and instead replaced with a fictitious "velocity" field obtained explicitly from the magnetic field, while the MHD induction equation is retained.…”

Section: Introductionmentioning

confidence: 99%

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Eruptivity Criteria for Solar Coronal Flux Ropes in Magnetohydrodynamic and Magnetofrictional Models

Rice,

Yeates

2023

ApJ

Self Cite

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We investigate which scalar quantity or quantities can best predict the loss of equilibrium and subsequent eruption of magnetic flux ropes in the solar corona. Our models are initialized with a potential magnetic arcade, which is then evolved by means of two effects on the lower boundary: first, a gradual shearing of the arcade, modeling differential rotation on the solar surface; and second, supergranular diffusion. These result in flux cancellation at the polarity inversion line and the formation of a twisted flux rope. We use three model setups: full magnetohydrodynamics (MHD) in cartesian coordinates, and the magnetofrictional (MF) model in both cartesian and polar coordinates. The flux ropes are translationally invariant, allowing for very fast computational times and thus a comprehensive parameter study, comprising hundreds of simulations and thousands of eruptions. Similar flux rope behavior is observed using either magnetofriction or MHD, and there are several scalar criteria that could be used as proxies for eruptivity. The most consistent predictor of eruptions in either model is the squared current in the axial direction of the rope, normalized by the relative helicity, although a variation on the previously proposed eruptivity index is also found to perform well in both the MF and MHD simulations.

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Effects of optimisation parameters on data-driven magnetofrictional modelling of active regions

Kumari¹,

Price²,

Daei³

et al. 2023

A&A

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Context. The solar magnetic field plays an essential role in the formation, evolution, and dynamics of large-scale eruptive structures in the corona. The estimation of the coronal magnetic field, the ultimate driver of space weather, particularly in the ‘low’ and ‘middle’ corona, is presently limited due to practical difficulties. Data-driven time-dependent magnetofrictional modelling (TMFM) of active region magnetic fields has been proven to be a useful tool to study the corona. The input to the model is the photospheric electric field that is inverted from a time series of the photospheric magnetic field. Constraining the complete electric field, that is, including the non-inductive component, is critical for capturing the eruption dynamics. We present a detailed study of the effects of optimisation of the non-inductive electric field on the TMFM of AR 12473. Aims. We aim to study the effects of varying the non-inductive electric field on the data-driven coronal simulations, for two alternative parametrisations. By varying parameters controlling the strength of the non-inductive electric field, we wish to explore the changes in flux rope formation and their early evolution and other parameters, for instance, axial flux and magnetic field magnitude. Methods. We used the high temporal and spatial resolution cadence vector magnetograms from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The non-inductive electric field component in the photosphere is critical for energising and introducing twist to the coronal magnetic field, thereby allowing unstable configurations to be formed. We estimated this component using an approach based on optimising the injection of magnetic energy. Results. Our data show that flux ropes are formed in all of the simulations except for those with the lower values of these optimised parameters. However, the flux rope formation, evolution and eruption time varies depending on the values of the optimisation parameters. The flux rope is formed and has overall similar evolution and properties with a large range of non-inductive electric fields needed to determine the non-inductive electric field component that is critical for energising and introducing twist to the coronal magnetic field. Conclusions. This study shows that irrespective of non-inductive electric field values, flux ropes are formed and erupted, which indicates that data-driven TMFM can be used to estimate flux rope properties early in their evolution without needing to employ a lengthy optimisation process.

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Eruptivity Criteria for Two-Dimensional Magnetic Flux Ropes in the Solar Corona

Cited by 5 publications

References 40 publications

Comparison of magnetic energy and helicity in coronal jet simulations

Comparison of magnetic energy and helicity in coronal jet simulations

Eruptivity Criteria for Solar Coronal Flux Ropes in Magnetohydrodynamic and Magnetofrictional Models

Effects of optimisation parameters on data-driven magnetofrictional modelling of active regions

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