Estimating the Magnetic Structure of an Erupting CME Flux Rope From AR12158 Using Data-Driven Modeling

We investigate here the magnetic properties of a large-scale magnetic flux rope related to a coronal mass ejection (CME) that erupted from the Sun on September 12, 2014 and produced a well-defined flux rope in interplanetary space on September 14–15, 2014. We apply a fully data-driven and time-dependent magnetofrictional method (TMFM) using Solar Dynamics Observatory (SDO) magnetograms as the lower boundary condition. The simulation self-consistently produces a coherent flux rope and its ejection from the simulation domain. This paper describes the identification of the flux rope from the simulation data and defining its key parameters (e.g., twist and magnetic flux). We define the axial magnetic flux of the flux rope and the magnetic field time series from at the apex and at different distances from the apex of the flux rope. Our analysis shows that TMFM yields axial magnetic flux values that are in agreement with several observational proxies. The extracted magnetic field time series do not match well with in-situ components in direct comparison presumably due to interplanetary evolution and northward propagation of the CME. The study emphasizes also that magnetic field time-series are strongly dependent on how the flux rope is intercepted which presents a challenge for space weather forecasting.

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A new technique for observationally derived boundary conditions for space weather

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2018012 ◽

2018 ◽

Vol 8 ◽

pp. A26 ◽

Cited By ~ 9

Author(s):

Paolo Pagano ◽

Duncan Hendry Mackay ◽

Anthony Robinson Yeates

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Boundary Conditions ◽

Space Weather ◽

Weather Forecasting ◽

Interplanetary Space ◽

Time Dependent ◽

Magnetic Flux Ropes ◽

Mhd Simulations ◽

Flux Ropes

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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A Model of Solar X-ray Bright Points and Ephemeral Active Regions

Australian Journal of Physics ◽

10.1071/ph790671 ◽

1979 ◽

Vol 32 (6) ◽

pp. 671 ◽

Cited By ~ 2

Author(s):

JH Piddington

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Large Scale ◽

Flux Rope ◽

Active Regions ◽

Activity Cycle ◽

Solar Magnetic Fields ◽

Flux Tubes ◽

X Ray ◽

Field System

Solar ephemeral active regions may provide a larger amount of emerging magnetic flux than the active regions themselves, and the origin and disposal of this flux pose problems. The related X-ray bright points are a major feature of coronal dynamics, and the two phenomena may entail a revision of our ideas of the activity cycle. A new large-scale subsurface magnetic field system has been suggested, but it is shown that such a system is neither plausible nor necessary. The emerging magnetic bipoles merely represent loops in pre-existing vertical flux tubes which are parts of active regions or the remnants of active regions. These loops result from the kink (or helical) instability in a twisted flux tube. Their observed properties are explained in terms of the flux-rope theory of solar fields. The model is extended to some dynamical effects in emerging loops. Further observations of ephemeral active regions may provide important tests between the traditional and flux-rope theories of solar magnetic fields.

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Data-driven MHD Simulation of the Formation and Initiation of a Large-scale Preflare Magnetic Flux Rope in AR 12371

The Astrophysical Journal ◽

10.3847/1538-4357/ab75ab ◽

2020 ◽

Vol 892 (1) ◽

pp. 9 ◽

Cited By ~ 1

Author(s):

Wen He ◽

Chaowei Jiang ◽

Peng Zou ◽

Aiying Duan ◽

Xueshang Feng ◽

...

Keyword(s):

Magnetic Flux ◽

Large Scale ◽

Flux Rope ◽

Data Driven ◽

Mhd Simulation ◽

Magnetic Flux Rope

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Effects of optimisation parameters on data-driven magnetofrictional modelling

10.5194/egusphere-egu21-9500 ◽

2021 ◽

Author(s):

Anshu Kumari ◽

Daniel Price ◽

Emilia Kilpua ◽

Jens Pomoell ◽

Farhad Daei

Keyword(s):

Magnetic Field ◽

Active Region ◽

Large Scale ◽

Magnetic Energy ◽

Flux Rope ◽

Coronal Magnetic Field ◽

Early Evolution ◽

Data Driven ◽

Magnetic Field Magnitude ◽

Mass Ejection

The solar coronal magnetic field plays an important role in the formation, evolution, and dynamics of small and large-scale structures in the corona. Estimation of the coronal magnetic field, the ultimate driver of space weather, particularly in the &#8216;low&#8217; and &#8216;middle&#8217; corona, is presently limited due to practical difficulties. Data-driven time-dependent magnetofrictional modelling (TMFM) of active region magnetic fields has been proven as a tool to observe and study the corona. In this work, we present a detailed study of data-driven TMFM of active region 12473 to trace the early evolution of the flux rope related to the coronal mass ejection that occurred on 28 December 2015. Non-inductive electric field component in the photosphere is critical for energizing and introducing twist to the coronal magnetic field, thereby allowing unstable configurations to be formed. We estimate this component using an approach based on optimizing the injection of magnetic energy. We study the effects of these optimisation parameters on the data driven coronal simulations. By varying the free optimisation parameters, we explore the changes in flux rope formation and their early evolution, as well other parameters, e.g. axial flux, magnetic field magnitude.

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Modeling Magnetic Flux Ropes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313010843 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 121-124

Author(s):

Chun Xia ◽

Rony Keppens

Keyword(s):

Magnetic Flux ◽

Large Scale ◽

Thermal Structure ◽

Three Dimensional ◽

Lower Boundary ◽

Flux Rope ◽

Mhd Simulation ◽

Magnetic Flux Rope ◽

Polarity Inversion ◽

Magnetic Flux Ropes

AbstractThe magnetic configuration hosting prominences can be a large-scale helical magnetic flux rope. As a necessary step towards future prominence formation studies, we report on a stepwise approach to study flux rope formation. We start with summarizing our recent three-dimensional (3D) isothermal magnetohydrodynamic (MHD) simulation where a flux rope is formed, including gas pressure and gravity. This starts from a static corona with a linear force-free bipolar magnetic field, altered by lower boundary vortex flows around the main polarities and converging flows towards the polarity inversion. The latter flows induce magnetic reconnection and this forms successive new helical loops so that a complete flux rope grows and ascends. After stopping the driving flows, the system relaxes to a stable helical magnetic flux rope configuration embedded in an overlying arcade. Starting from this relaxed isothermal endstate, we next perform a thermodynamic MHD simulation with a chromospheric layer inserted at the bottom. As a result of a properly parametrized coronal heating, and due to radiative cooling and anisotropic thermal conduction, the system further relaxes to an equilibrium where the flux rope and the arcade develop a fully realistic thermal structure. This paves the way to future simulations for 3D prominence formation.

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Constraining the CME parameters of the spheromak flux rope implemented in EUHFORIA

10.5194/egusphere-egu21-3291 ◽

2021 ◽

Author(s):

Eleanna Asvestari ◽

Jens Pomoell ◽

Emilia Kilpua ◽

Simon Good ◽

Theodosios Chatzistergos ◽

...

Keyword(s):

Magnetic Field ◽

Space Weather ◽

Weather Forecasting ◽

Interplanetary Space ◽

Source Region ◽

Flux Rope ◽

Field Configuration ◽

Arrival Times ◽

Sheath Region ◽

Region Length

Coronal mass ejections (CMEs) are primary drivers of space weather phenomena. Modelling the evolution of the internal magnetic field configuration of CMEs as they propagate through the interplanetary space is an essential part of space weather forecasting. EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is a data-driven, physics-based model, able to trace the evolution of CMEs and CME-driven shocks through realistic background solar wind conditions. It employs a spheromak-type magnetic flux rope that is initially force-free, providing it with the advantage of modelling CME as magnetised structures. For this work we assessed the spheromak CME model employed in EUHFORIA with a test CME case study. The selected CME eruption occurred on the 6th of January 2013 and was encountered by two spacecraft, Venus Express and STEREO--A, which were radially aligned at the time of the CME passage. Our focus was to constrain the input parameters, with particular interest in: (1) translating the angular widths of the graduated cylindrical shell (GCS) fitting to the spheromak radius, and (2) matching the observed magnetic field topology at the source region. We ran EUHFORIA with three different spheromak radii. The model predicts arrival times from half to a full day ahead of the one observed in situ. We conclude that the choice of spheromak radius affected the modelled magnetic field profiles, their amplitude, arrival times, and sheath region length.

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Magnetic field transport in compact binaries

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037903 ◽

2020 ◽

Vol 641 ◽

pp. A133

Author(s):

N. Scepi ◽

G. Lesur ◽

G. Dubus ◽

J. Jacquemin-Ide

Keyword(s):

Magnetic Field ◽

Angular Momentum ◽

Magnetic Flux ◽

Large Scale ◽

Compact Object ◽

Light Curves ◽

Momentum Transport ◽

Local Magnetization ◽

Angular Momentum Transport ◽

The Impact

Context. Dwarf novæ (DNe) and low mass X-ray binaries (LMXBs) show eruptions that are thought to be due to a thermal-viscous instability in their accretion disk. These eruptions provide constraints on angular momentum transport mechanisms. Aims. We explore the idea that angular momentum transport could be controlled by the dynamical evolution of the large-scale magnetic field. We study the impact of different prescriptions for the magnetic field evolution on the dynamics of the disk. This is a first step in confronting the theory of magnetic field transport with observations. Methods. We developed a version of the disk instability model that evolves the density, the temperature, and the large-scale vertical magnetic flux simultaneously. We took into account the accretion driven by turbulence or by a magnetized outflow with prescriptions taken, respectively, from shearing box simulations or self-similar solutions of magnetized outflows. To evolve the magnetic flux, we used a toy model with physically motivated prescriptions that depend mainly on the local magnetization β, where β is the ratio of thermal pressure to magnetic pressure. Results. We find that allowing magnetic flux to be advected inwards provides the best agreement with DNe light curves. This leads to a hybrid configuration with an inner magnetized disk, driven by angular momentum losses to an MHD outflow, sharply transiting to an outer weakly-magnetized turbulent disk where the eruptions are triggered. The dynamical impact is equivalent to truncating a viscous disk so that it does not extend down to the compact object, with the truncation radius dependent on the magnetic flux and evolving as Ṁ−2/3. Conclusions. Models of DNe and LMXB light curves typically require the outer, viscous disk to be truncated in order to match the observations. There is no generic explanation for this truncation. We propose that it is a natural outcome of the presence of large-scale magnetic fields in both DNe and LMXBs, with the magnetic flux accumulating towards the center to produce a magnetized disk with a fast accretion timescale.

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Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby

10.5194/egusphere-egu21-3424 ◽

2021 ◽

Author(s):

Wei-Jie Sun ◽

James Slavin ◽

Rumi Nakamura ◽

Daniel Heyner ◽

Johannes Mieth

Keyword(s):

Magnetic Field ◽

Large Scale ◽

European Space Agency ◽

Flux Rope ◽

Transfer Event ◽

Flux Transfer Events ◽

Space Agency ◽

Flux Ropes ◽

Flux Transfer ◽

Magnetospheric Multiscale Mission

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the &#160;flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees. &#160;As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.

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Modeling the magnetic structure of CMEs in the inner heliosphere based on data-driven time-dependent simulations of active region evolution

10.5194/egusphere-egu21-13048 ◽

2021 ◽

Author(s):

Jens Pomoell ◽

Emilia Kilpua ◽

Daniel Price ◽

Eleanna Asvestari ◽

Ranadeep Sarkar ◽

...

Keyword(s):

Magnetic Field ◽

Active Region ◽

Magnetic Structure ◽

Interplanetary Space ◽

Coronal Magnetic Field ◽

Time Dependent ◽

Data Driven ◽

Dependent Data ◽

Heliospheric Physics ◽

The Magnetic Field

Characterizing the detailed structure of the magnetic field in the active corona is of crucial importance for determining the chain of events from the formation to the destabilisation and subsequent eruption and propagation of coronal structures in the heliosphere. A comprehensive methodology to address these dynamic processes is needed in order to advance our capabilities to predict the properties of coronal mass ejections (CMEs) in interplanetary space and thereby for increasing the accuracy of space weather predictions. A promising toolset to provide the key missing information on the magnetic structure of CMEs are time-dependent data-driven simulations of active region magnetic fields. This methodology permits self-consistent modeling of the evolution of the coronal magnetic field from the emergence of flux to the birth of the eruption and beyond.&#160;In this presentation, we discuss our modeling efforts in which time-dependent data-driven coronal modeling together with heliospheric physics-based modeling are employed to study and characterize CMEs, in particular their magnetic structure, at various stages in their evolution from the Sun to Earth.&#160;

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