scholarly journals Initiation of Coronal Mass Ejections by Sunspot Rotation

2013 ◽  
Vol 8 (S300) ◽  
pp. 201-208
Author(s):  
G. Valori ◽  
T. Török ◽  
M. Temmer ◽  
A. M. Veronig ◽  
L. van Driel-Gesztelyi ◽  
...  
Keyword(s):  
Potential Field ◽  
Flux Distribution ◽  
Three Dimensional ◽  
Flux Rope ◽  
Second Phase ◽  
Clockwise Rotation ◽  
Mhd Simulations ◽  
Magnetic Tension ◽  
Mass Ejection ◽  
The Magnetic Field

AbstractWe report observations of a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in Active Region NOAA 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux rope, using three-dimensional zero–β MHD simulations. We consider a magnetic configuration whose photospheric flux distribution and coronal structure is guided by the observations and a potential field extrapolation. We find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux rope enters an unstable regime characterized by a strong acceleration. Our simulation thus suggests a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots.

scholarly journals A distinct magnetic property of the inner penumbral boundary

2020 ◽  
Vol 638 ◽  
pp. A28 ◽  
Author(s):  
Jan Jurčák ◽  
Markus Schmassmann ◽  
Matthias Rempel ◽  
Nazaret Bello González ◽  
Rolf Schlichenmaier
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Magnetic Property ◽  
Potential Field ◽  
Magnetic Energy ◽  
Vertical Component ◽  
Flux Rope ◽  
Field Configuration ◽  
The Magnetic Field ◽  
Upper Boundary

Context. Analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary: the invariance of the vertical component of the magnetic field. Aims. We analyse the magnetic properties of the umbra-penumbra boundary in simulated sunspots and thus assess their similarity to observed sunspots. We also aim to investigate the role of the plasma β and the ratio of kinetic to magnetic energy in simulated sunspots in the convective motions because these quantities cannot be reliably determined from observations. Methods. We used a set of non-gray simulation runs of sunspots with the MURaM code. The setups differed in terms of subsurface magnetic field structure and magnetic field boundary imposed at the top of the simulation domain. These data were used to synthesize the Stokes profiles, which were then degraded to the Hinode spectropolarimeter-like observations. Then, the data were treated like real Hinode observations of a sunspot, and magnetic properties at the umbral boundaries were determined. Results. Simulations with potential field extrapolation produce a realistic magnetic field configuration on the umbral boundaries of the sunspots. Two simulations with a potential field upper boundary, but different subsurface magnetic field structures, differ significantly in the extent of their penumbrae. Increasing the penumbra width by forcing more horizontal magnetic fields at the upper boundary results in magnetic properties that are not consistent with observations. This implies that the size of the penumbra is given by the subsurface structure of the magnetic field, that is, by the depth and inclination of the magnetopause, which is shaped by the expansion of the sunspot flux rope with height. None of the sunspot simulations is consistent with the observed properties of the magnetic field and the direction of the Evershed flow at the same time. Strong outward-directed Evershed flows are only found in setups with an artificially enhanced horizontal component of the magnetic field at the top boundary that are not consistent with the observed magnetic field properties at the umbra-penumbra boundary. We stress that the photospheric boundary of simulated sunspots is defined by a magnetic field strength of equipartition field value.

Predicting geo-effectiveness of CMEs using a novel 3D CME model FRi3D integrated into EUHFORIA 

2021 ◽  
Author(s):  
Stefaan Poedts ◽  
Anwesha Maharana ◽  
Camilla Scolini ◽  
Alexey Isavnin
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Three Dimensional ◽  
Flux Rope ◽  
Future Perspective ◽  
The European Union ◽  
Horizon 2020 ◽  
The Magnetic Field

<p>Previous studies of Coronal Mass Ejections (CMEs) have shown the importance of understanding their geometrical structure and internal magnetic field configuration for improving forecasting at Earth. The precise prediction of the CME shock and the magnetic cloud arrival time, their magnetic field strength and the orientation upon impact at Earth is still challenging and relies on solar wind and CME evolution models and precise input parameters. In order to understand the propagation of CMEs in the interplanetary medium, we need to understand their interaction with the complex features in the magnetized background solar wind which deforms, deflects and erodes the CMEs and determines their geo-effectiveness. Hence, it is important to model the internal magnetic flux-rope structure in the CMEs as they interact with CIRs/SIRs, other CMEs and solar transients in the heliosphere. The spheromak model (Verbeke et al. 2019) in the heliospheric wind and CME evolution simulation EUHFORIA (Pomoell and Poedts, 2018), fits well with the data near the CME nose close to its axis but fails to predict the magnetic field in CME legs when these impact Earth (Scolini et al. 2019). Therefore, we implemented the FRi3D stretched flux-rope CME model (Isavnin, 2016) in EUHFORIA to model a more realistic CME geometry. Fri3D captures the three-dimensional magnetic field structure with parameters like skewing, pancaking and flattening that quantify deformations experienced by an interplanetary CME. We perform test runs of real CME events and validate the ability of FRi3D coupled with EUHFORIA in predicting the CME geo-effectiveness. We have modeled two real events with FRi3D. First, a CME event on 12 July 2012 which was a head-on encounter at Earth. Second, the flank CME encounter of 14 June 2012 which did not leave any magnetic field signature at Earth when modeled with Spheromak. We compare our results with the results from non-magnetized cone simulations and magnetized simulations employing the spheromak flux-rope model. We further discuss how constraining observational parameters using the stretched flux rope CME geometry in FRi3D affects the prediction of the magnetic field strength in our simulations, highlighting improvements and discussing future perspective.</p><p><em>This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0)</em></p>

scholarly journals Shearing motions and torus instability in the 2010 April 3 filament eruption

2013 ◽  
Vol 8 (S300) ◽  
pp. 475-476
Author(s):  
F. P. Zuccarello ◽  
P. Romano ◽  
F. Zuccarello ◽  
S. Poedts
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Flux Rope ◽  
Active Region Noaa ◽  
Axial Field ◽  
Drift Motion ◽  
Filament Eruption ◽  
Onset Condition ◽  
Mass Ejection ◽  
The Magnetic Field

AbstractThe magnetic field evolution of active region NOAA 11059 is studied in order to determine the possible causes and mechanisms that led to the initiation of the 2010 April 3 coronal mass ejection (CME).We find (1) that the magnetic configuration of the active region is unstable to the torus instability and (2) that persistent shearing motions characterized the negative polarity, resulting in a southward, almost parallel to the meridians, drift motion of the negative magnetic field concentrations.We conclude that these shearing motions increased the axial field of the filament eventually bringing the flux rope axis to a height where the onset condition for the torus instability was satisfied.

scholarly journals The role of streamers in the deflection of coronal mass ejections

2011 ◽  
Vol 7 (S286) ◽  
pp. 134-138
Author(s):  
F. P. Zuccarello ◽  
A. Bemporad ◽  
C. Jacobs ◽  
M. Mierla ◽  
S. Poedts ◽  
...  
Keyword(s):  
Current Sheet ◽  
Three Dimensional ◽  
Heliospheric Current Sheet ◽  
Field Of View ◽  
Physical Explanation ◽  
Filament Eruption ◽  
Mhd Simulations ◽  
Radial Evolution ◽  
Mass Ejection

AbstractOn 2009 September 21, a filament eruption and the associated Coronal Mass Ejection (CME) was observed by the STEREO spacecraft. The CME originated from the southern hemisphere and showed a deflection of about 15° towards the heliospheric current sheet (HCS) during its propagation in the COR1 field-of-view (FOV). The aim of this paper is to provide a physical explanation for the strong deflection of the CME. We first use the STEREO observations in order to reconstruct the three dimensional (3D) trajectory of the CME. Starting from a magnetic configuration that closely resembles the potential field extrapolation for that date, we performed numerical magneto-hydrodynamics (MHD) simulations. By applying localized shearing motions, a CME is initiated in the simulation, showing a similar non-radial evolution, structure, and velocity as the observed event. The CME gets deflected towards the current sheet of the larger northern helmet streamer, due to an imbalance in the magnetic pressure and tension forces and finally it gets into the streamer and propagates along the heliospheric current sheet.

scholarly journals The early Earth under a superflare and super-CME attack: prospects for life

2015 ◽  
Vol 11 (S320) ◽  
pp. 409-415 ◽  
Author(s):  
Vladimir Airapetian ◽  
Alex Glocer ◽  
Guillaume Gronoff
Keyword(s):  
Molecular Nitrogen ◽  
Three Dimensional ◽  
Solar Energetic Particle ◽  
Early Earth ◽  
Polar Cap ◽  
Mhd Simulations ◽  
The Earth ◽  
The Origin Of Life ◽  
Mass Ejection ◽  
The Impact

AbstractKepler observations suggest that G-type stars produce powerful flares suggesting that the early Earth may also have been exposed to frequent and energetic solar explosive events generated by the young Sun. We show that powerful coronal mass ejection (CME) events associated with superflares impacting the Earth magnetosphere with a frequency of 1 event/day. What was the impact of superflares, CMEs and associated solar energetic particle (SEPs) events on the atmospheric erosion of the young Earth and habitability? In this paper we discuss our three-dimensional (3D) magnetohydrodynamic (MHD) simulations that show that frequent and energetic CMEs from the early Sun continuously destroyed the sub-solar parts of Earth's magnetosphere at heights < 1.25 RE. This suggests that CME shock accelerated energetic protons are capable of penetrating into the polar cap region and breaking atmospheric molecular nitrogen, the major ingredient of the early Earth atmosphere, into atomic nitrogen. Photo-collisional dissociation of molecular nitrogen and carbon dioxide creates reactive chemistry that efficiently produces nitrous oxide and hydrogen cyanide, the essential molecule in prebiotic life chemistry. This raises an possibility that frequent super-CMEs could serve as a potential catalyst for the origin of life on early Earth.

scholarly journals New data-driven method of simulating coronal mass ejections

2019 ◽  
Vol 626 ◽  
pp. A91 ◽  
Author(s):  
Cheng’ao Liu ◽  
Tao Chen ◽  
Xinhua Zhao
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejections ◽  
Three Dimensional ◽  
Flux Rope ◽  
Mhd Equations ◽  
Data Driven ◽  
Flux Emergence ◽  
Polarity Inversion ◽  
Polarity Inversion Line ◽  
The Magnetic Field

Context. Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic field from the Sun’s corona. Understanding the evolution of the CME is important to evaluate its impact on space weather. Using numerical simulation, we are able to reproduce the occurrence and evolution process of the CME. Aims. The aim of this paper is to provide a new data-driven method to mimic the coronal mass ejections. By using this method, we can investigate the phsical mechanisms of the flux rope formation and the cause of the CME eruption near the real background. Methods. Starting from a potential magnetic field extrapolation, we have solved a full set of magnetohydrodynamic (MHD) equations by using the conservation element and solution element (CESE) numerical method. The bottom boundary is driven by the vector magnetograms obtained from SDO/HMI and vector velocity maps derived from DAVE4VM method. Results. We present a three-dimensional numerical MHD data-driven model for the simulation of the CME that occurred on 2015 June 22 in the active region NOAA 12371. The numerical results show two elbow-shaped loops formed above the polarity inversion line (PIL), which is similar to the tether-cutting picture previously proposed. The temporal evolutions of magnetic flux show that the sunspots underwent cancellation and flux emergence. The signature of velocity field derived from the tracked magnetograms indicates the persistent shear and converging motions along the PIL. The simulation shows that two elbow-shaped loops were reconnected and formed an inverse S-shaped sigmoid, suggesting the occurrence of the tether-cutting reconnection, which was supported by observations of the Atmospheric Imaging Assembly (AIA) telescope. Analysis of the decline rate of the magnetic field indicates that the flux rope reached a region where the torus instability was triggered. Conclusions. We conclude that the eruption of this CME was caused by multiple factors, such as photosphere motions, reconnection, and torus instability. Moreover, our simulation successfully reproduced the three-component structures of typical CMEs.

scholarly journals Numerical simulation of helical jets at active region peripheries

2019 ◽  
Vol 490 (3) ◽  
pp. 3679-3690 ◽  
Author(s):  
Peter F Wyper ◽  
C Richard DeVore ◽  
Spiro K Antiochos
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Three Dimensional ◽  
Flux Rope ◽  
Active Regions ◽  
Quantitative Agreement ◽  
Null Point ◽  
Closed Field ◽  
The Magnetic Field ◽  
Bald Patch

ABSTRACT Coronal jets are observed above minority-polarity intrusions throughout the solar corona. Some of the most energetic ones occur on the periphery of active regions where the magnetic field is strongly inclined. These jets exhibit a non-radial propagation in the low corona as they follow the inclined field, and often have a broad, helical shape. We present a three-dimensional magnetohydrodynamic simulation of such an active-region-periphery helical jet. We consider an initially potential field with a bipolar flux distribution embedded in a highly inclined magnetic field, representative of the field nearby an active region. The flux of the minority polarity sits below a bald-patch separatrix initially. Surface motions are used to inject free energy into the closed field beneath the separatrix, forming a sigmoidal flux rope that eventually erupts producing a helical jet. We find that a null point replaces the bald patch early in the evolution and that the eruption results from a combination of magnetic breakout and an ideal kinking of the erupting flux rope. We discuss how the two mechanisms are coupled, and compare our results with previous simulations of coronal-hole jets. This comparison supports the hypothesis that the generic mechanism for all coronal jets is a coupling between breakout reconnection and an ideal instability. We further show that our results are in good qualitative and quantitative agreement with observations of active-region-periphery jets.

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

Reduced MHD in nearly potential magnetic fields

1997 ◽  
Vol 57 (1) ◽  
pp. 83-87 ◽  
Author(s):  
H. R. STRAUSS
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Potential Field ◽  
Three Dimensional ◽  
Pressure Effects ◽  
Mhd Equations ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
The Magnetic Field

Reduced, approximate MHD equations are derived for the case where the magnetic field is close to a potential field. The potential field can have an arbitrary three-dimensional structure, as long as it is non-vanishing. Finite current and pressure effects are included.

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