scholarly journals Modeling Magnetic Flux Ropes

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.

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

2020 ◽  
Vol 892 (1) ◽  
pp. 9 ◽  
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

scholarly journals Hydrogen non-equilibrium ionisation effects in coronal mass ejections

2020 ◽  
Vol 637 ◽  
pp. A49
Author(s):  
P. Pagano ◽  
A. Bemporad ◽  
D. H. Mackay
Keyword(s):  
Magnetic Flux ◽  
Visible Light ◽  
Coronal Mass Ejections ◽  
Flux Rope ◽  
Neutral Hydrogen ◽  
Hydrogen Atoms ◽  
Mhd Simulation ◽  
Magnetic Flux Rope ◽  
New Generation ◽  
Non Equilibrium

Context. A new generation of coronagraphs used to study solar wind and coronal mass ejections (CMEs) are being developed and launched. These coronagraphs will heavily rely on multi-channel observations where visible light (VL) and UV-EUV (ultraviolet-extreme ultraviolet) observations provide new plasma diagnostics. One of these instruments, Metis on board ESA-Solar Orbiter, will simultaneously observe VL and the UV Lyman-α line. The number of neutral hydrogen atoms (a small fraction of coronal protons) is a key parameter for deriving plasma properties, such as the temperature from the observed Lyman-α line intensity. However, these measurements are significantly affected if non-equilibrium ionisation effects occur, which can be relevant during CMEs. Aims. The aim of this work is to determine if non-equilibrium ionisation effects are relevant in CMEs and, in particular, when and in which regions of the CME plasma ionisation equilibrium can be assumed for data analysis. Methods. We used a magneto-hydrodynamic (MHD) simulation of a magnetic flux rope ejection to generate a CME. From this, we then reconstructed the ionisation state of hydrogen atoms in the CME by evaluating both the advection of neutral and ionised hydrogen atoms and the ionisation and recombination rates in the MHD simulation. Results. We find that the equilibrium ionisation assumption mostly holds in the core of the CME, which is represented by a magnetic flux rope. In contrast, non-equilibrium ionisation effects are significant at the CME front, where we find about 100 times more neutral hydrogen atoms than prescribed by ionisation equilibrium conditions. We find this to be the case even if this neutral hydrogen excess might be difficult to identify due to projection effects. Conclusions. This work provides key information for the development of a new generation of diagnostic techniques that aim to combine visible light and Lyman-α line emissions. The results show that non-equilibrium ionisation effects need to be considered when we analyse CME fronts. Incorrectly assuming equilibrium ionisation in these regions would lead to a systematic underestimate of plasma temperatures.

Structure and Evolution of an Inter–Active Region Large-scale Magnetic Flux Rope

2021 ◽  
Vol 906 (1) ◽  
pp. 45
Author(s):  
Aiying Duan ◽  
Chaowei Jiang ◽  
Peng Zou ◽  
Xueshang Feng ◽  
Jun Cui
Keyword(s):  
Active Region ◽  
Magnetic Flux ◽  
Large Scale ◽  
Flux Rope ◽  
Magnetic Flux Rope

scholarly journals Structure and Topology of Magnetic Fields in Solar Prominences

2013 ◽  
Vol 8 (S300) ◽  
pp. 127-134 ◽  
Author(s):  
Adriaan A. van Ballegooijen ◽  
Yingna Su
Keyword(s):  
Magnetic Flux ◽  
Flux Rope ◽  
Time Dependent ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
And Topology ◽  
Solar Prominences ◽  
Magnetic Elements ◽  
Dependent Model ◽  
Time Dependent Model

AbstractRecent observations and models of solar prominences are reviewed. The observations suggest that prominences are located in or below magnetic flux ropes that lie horizontally above the PIL. However, the details of the magnetic structure are not yet fully understood. Gravity likely plays an important role in shaping the vertical structures observed in quiescent prominences. Preliminary results from a time-dependent model describing the interaction of a magnetic flux rope with photospheric magnetic elements are presented.

scholarly journals Microwave indicator of potential geoeffectiveness and magnetic flux-rope structure of a solar active region

2021 ◽  
Vol 7 (1) ◽  
pp. 3-12
Author(s):  
Anastasiia Kudriavtseva ◽  
Ivan Myshyakov ◽  
Arkadiy Uralov ◽  
Victor Grechnev
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Neutral Line ◽  
Flux Rope ◽  
Coronal Magnetic Field ◽  
Horizontal Magnetic Field ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
Class Flare

We analyze the presence of a microwave neutral-line-associated source (NLS) in a super-active region NOAA 12673, which produced a number of geo-effective events in September 2017. To estimate the NLS position, we use data from the Siberian Radioheliograph in a range 4–8 GHz and from the Nobeyama Radioheliograph at 17 GHz. Calculation of the coronal magnetic field in a non-linear force-free approximation has revealed an extended structure consisting of interconnected magnetic flux ropes, located practically along the entire length of the main polarity separation line of the photospheric magnetic field. NLS is projected into the region of the strongest horizontal magnetic field, where the main energy of this structure is concentrated. During each X-class flare, the active region lost magnetic helicity and became a CME source.

The magnetic flux rope structure of coronal mass ejections – 2021 Julius Bartels Medal Lecture at vEGU

2021 ◽  
Author(s):  
Volker Bothmer
Keyword(s):  
Magnetic Flux ◽  
White Light ◽  
Coronal Mass Ejections ◽  
Large Scale ◽  
Neutral Line ◽  
Source Region ◽  
Flux Rope ◽  
Magnetic Clouds ◽  
Small Scale ◽  
Magnetic Flux Rope

<div> <p><span>Magnetic clouds are transient solar wind flows in the interplanetary medium with smooth rotations of the magnetic field vector and low plasma beta values. The analysis of magnetic clouds identified in the data of the two Helios spacecraft between 0.3 and 1 AU showed that they can be interpreted to first order by force-free, large-scale, cylindrical magnetic flux tubes. A close correlation of their occurrences was found with disappearing filaments at the Sun. The magnetic clouds that originated from the northern solar hemisphere showed predominantly left-handed magnetic helicities and the ones from the southern hemisphere predominantly right-handed ones. They were often preceded by an interplanetary shock wave and some were found to be directly following a coronal mass ejection towards the Helios spacecraft as detected by the Solwind coronagraph on board the P78-1 satellite. With the SOHO mission unprecedented long-term observations of coronal mass ejections (CMEs) were taken with the LASCO coronagraphs, with a spatial and time resolution that allowed to investigate their internal white-light fine structure. With complementary photospheric and EUV observations from SOHO, CMEs were found to arise from pre-existing small scale loop systems, overlying regions of opposite magnetic polarities. From the characteristic pattern of their source regions in both solar hemispheres, a generic scheme was presented in which their projected white-light topology depends primarily on the orientation and position of the source region’s neutral line on the solar disk. Based on this interpretation the graduated cylindrical shell method was developed, which allowed to model the electron density distribution of CMEs as 3D flux ropes. This concept was validated through stereoscopic observations of CMEs taken by the coronagraphs of the SECCHI remote sensing suite on board the twin STEREO spacecraft. The observations further revealed that the dynamic near-Sun evolution of CMEs often leads to distortions of their flux rope structure. However, the magnetic flux rope concept of CMEs is today one of the fundamental methods in space weather forecasts. With the Parker Solar Probe we currently observe for the first time CMEs in-situ and remotely at their birthplaces in the solar corona and can further unravel their origin and evolution from the corona into the heliosphere. This lecture provides a state-of-the-art overview on the magnetic structure of CMEs and includes latest observations from the Parker Solar Probe mission.</span></p> </div>

scholarly journals Mass ejections from the Sun

2015 ◽  
Vol 11 (S320) ◽  
pp. 211-217
Author(s):  
Lucie M. Green
Keyword(s):  
Magnetic Flux ◽  
Coronal Mass Ejection ◽  
Flux Rope ◽  
Remote Sensing Data ◽  
Active Regions ◽  
Theoretical Models ◽  
Field Configuration ◽  
Magnetic Flux Rope ◽  
Magnetic Flux Ropes ◽  
Mass Ejection

AbstractCoronal mass ejections are the most spectacular form of solar activity and they play a key role in driving space weather at the Earth. These eruptions are associated with active regions and occur throughout an active region's entire lifetime. All coronal mass ejection models invoke the presence of a twisted magnetic field configuration known as a magnetic flux rope either before or after eruption onset. The observational identification of magnetic flux ropes in the solar atmosphere using remote sensing data represents a challenging task, but theoretical models have led to the understanding that there are signatures that reveal their presence. The range of coronal mass ejection models are helping build a more complete picture of both the trigger and drivers of these eruptions.

scholarly journals Three-dimensional MHD Simulations of Solar Prominence Oscillations in a Magnetic Flux Rope

2018 ◽  
Vol 856 (2) ◽  
pp. 179 ◽  
Author(s):  
Yu-Hao Zhou ◽  
C. Xia ◽  
R. Keppens ◽  
C. Fang ◽  
P. F. Chen
Keyword(s):  
Magnetic Flux ◽  
Three Dimensional ◽  
Flux Rope ◽  
Solar Prominence ◽  
Magnetic Flux Rope ◽  
Mhd Simulations
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