scholarly journals The role of non-axisymmetry of magnetic flux rope in constraining solar eruptions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ze Zhong ◽  
Yang Guo ◽  
M. D. Ding
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Flux Rope ◽  
Radial Magnetic Field ◽  
Magnetic Flux Rope ◽  
Background Magnetic Field ◽  
Solar Eruptions ◽  
Magnetohydrodynamic Simulation ◽  
Mass Ejection

AbstractWhether a solar eruption is successful or failed depends on the competition between different components of the Lorentz force exerting on the flux rope that drives the eruption. The present models only consider the strapping force generated by the background magnetic field perpendicular to the flux rope and the tension force generated by the field along the flux rope. Using the observed magnetic field on the photosphere as a time-matching bottom boundary, we perform a data-driven magnetohydrodynamic simulation for the 30 January 2015 confined eruption and successfully reproduce the observed solar flare without a coronal mass ejection. Here we show a Lorentz force component, resulting from the radial magnetic field or the non-axisymmetry of the flux rope, which can essentially constrain the eruption. Our finding contributes to the solar eruption model and presents the necessity of considering the topological structure of a flux rope when studying its eruption behaviour.

scholarly journals Pressure enhancement associated with meridional flow in high-speed solar wind: possible evidence for an interplanetary magnetic flux rope

1997 ◽  
Vol 15 (2) ◽  
pp. 137-142 ◽  
Author(s):  
C.-Y. Tu ◽  
E. Marsch ◽  
K. Ivory ◽  
R. Schwenn
Keyword(s):  
Magnetic Field ◽  
Angular Distribution ◽  
Magnetic Flux ◽  
High Speed ◽  
Electron Distribution Function ◽  
Flux Rope ◽  
Pressure Rise ◽  
High Energy ◽  
Magnetic Flux Rope ◽  
Background Magnetic Field

Abstract. A sizable total-pressure (magnetic pressure plus kinetic pressure) enhancement was found within the high-speed wind stream observed by Helios 2 in 1976 near 0.3 AU. The proton density and temperature and the magnetic magnitude simultaneously increased for about 6 h. This pressure rise was associated with a comparatively large southward flow velocity component (with Vz ≈ –100 km · s–1) and magnetic-field rotation. The pressure enhancement was associated with unusual features in the electron distribution function. It shows a wide angular distribution of electron counting rates in the low-energy (57.8 eV) channel, while previous to the enhancement it exhibits a wide angular distribution of electron count rate in the high-energy (112, 221 and 309 eV) channels, perhaps indicating the mirroring of electrons in the converging field lines of the background magnetic field. These fluid and kinetic phenomena may be explained as resulting from an interplanetary magnetic flux rope which is not fully convected by the flow but moves against the background wind towards the Sun.

scholarly journals Magnetic field topology from non-force free extrapolation and magnetohydrodynamic simulation of its eventual dynamics

2018 ◽  
Vol 13 (S340) ◽  
pp. 183-184
Author(s):  
Sushree S. Nayak ◽  
R. Bhattacharyya ◽  
A. Prasad ◽  
Q. Hu
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Free Field ◽  
Magnetic Field Topology ◽  
Mhd Simulations ◽  
Extrapolation Scheme ◽  
Magnetohydrodynamic Simulation ◽  
Force Free Field ◽  
Contemporary Standard

AbstractMagnetic reconnections (MRs) for various magnetic field line (MFL) topologies are believed to be the initiators of solar eruptive events like flares and coronal mass ejections (CMEs). Consequently, important is a thorough understanding and quantification of the MFL topology and their evolution which leads to MRs. Contemporary standard is to extrapolate the coronal MFLs using equilibrium models where the Lorentz force on the coronal plasma is zero everywhere. In tandem, a non-force-free-field (NFFF) extrapolation scheme has evolved and allows for a Lorentz force which is non-zero only at the photosphere but asymptotically vanishes with height. The paper reports magnetohydrodynamic (MHD)- simulations initiated by NFFF extrapolation of the coronal MFLs for a flare producing active region NOAA 11158. Interestingly, quasi-separatrix layers (QSLs) which facilitate MRs are detected in the extrapolated MFLs and, here the paper makes an attempt to asses the role of QSLs in the flare onsets.

scholarly journals Relative magnetic helicity as a diagnostic of solar eruptivity

2017 ◽  
Vol 601 ◽  
pp. A125 ◽  
Author(s):  
E. Pariat ◽  
J. E. Leake ◽  
G. Valori ◽  
M. G. Linton ◽  
F. P. Zuccarello ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Magnetic Energy ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flux Rope ◽  
Magnetic Helicity ◽  
Free Energies ◽  
Magnetic Flux Rope ◽  
Solar Eruptions

Context. The discovery of clear criteria that can deterministically describe the eruptive state of a solar active region would lead to major improvements on space weather predictions. Aims. Using series of numerical simulations of the emergence of a magnetic flux rope in a magnetized coronal, leading either to eruptions or to stable configurations, we test several global scalar quantities for the ability to discriminate between the eruptive and the non-eruptive simulations. Methods. From the magnetic field generated by the three-dimensional magnetohydrodynamical simulations, we compute and analyze the evolution of the magnetic flux, of the magnetic energy and its decomposition into potential and free energies, and of the relative magnetic helicity and its decomposition. Results. Unlike the magnetic flux and magnetic energies, magnetic helicities are able to markedly distinguish the eruptive from the non-eruptive simulations. We find that the ratio of the magnetic helicity of the current-carrying magnetic field to the total relative helicity presents the highest values for the eruptive simulations, in the pre-eruptive phase only. We observe that the eruptive simulations do not possess the highest value of total magnetic helicity. Conclusions. In the framework of our numerical study, the magnetic energies and the total relative helicity do not correspond to good eruptivity proxies. Our study highlights that the ratio of magnetic helicities diagnoses very clearly the eruptive potential of our parametric simulations. Our study shows that magnetic-helicity-based quantities may be very efficient for the prediction of solar eruptions.

Observations for the Role of Flux rope Eruption in a Geoeffective Solar Flare

2014 ◽  
Vol 4 (2) ◽  
pp. 555-564
Author(s):  
A.M Aslam
Keyword(s):  
Solar Flare ◽  
Flux Rope ◽  
Magnetic Configuration ◽  
Solar Dynamics Observatory ◽  
Multi Wavelength ◽  
Solar Dynamics ◽  
Halo Coronal Mass Ejection ◽  
Mass Ejection ◽  
The Waves

On September 24, 2011 a solar flare of M 7.1 class was released from the Sun. The flare was observed by most of the space and ground based observatories in various wavebands. We have carried out a study of this flare to understand its causes on Sun and impact on earth. The flare was released from NOAA active region AR 11302 at 12:33 UT. Although the region had already produced many M class flares and one X- class flare before this flare, the magnetic configuration was not relaxed and still continued to evolve as seen from HMI observations. From the Solar Dynamics Observatory (SDO) multi-wavelength (131 Ã…, 171 Ã…, 304 Ã… and 1600Ã…) observations we identified that a rapidly rising flux rope triggered the flare although HMI observations revealed that magnetic configuration did not undergo a much pronounced change. The flare was associated with a halo Coronal Mass Ejection (CME) as recorded by LASCO/SOHO Observations. The flare associated CME was effective in causing an intense geomagnetic storm with minimum Dst index -103 nT. A radio burst of type II was also recorded by the WAVES/WIND. In the present study attempt is made to study the nature of coupling between solar transients and geospace.

Connecting a Star’s Convection Zone with its Corona

1995 ◽  
Vol 12 (2) ◽  
pp. 180-185 ◽  
Author(s):  
D. J. Galloway ◽  
C. A. Jones
Keyword(s):  
Magnetic Field ◽  
Convection Zone ◽  
Flux Rope ◽  
Field System ◽  
Stellar Convection ◽  
Coronal Activity ◽  
Flux Concentration ◽  
Global Understanding ◽  
The Magnetic Field

AbstractThis paper discusses problems which have as their uniting theme the need to understand the coupling between a stellar convection zone and a magnetically dominated corona above it. Interest is concentrated on how the convection drives the atmosphere above, loading it with the currents that give rise to flares and other forms of coronal activity. The role of boundary conditions appears to be crucial, suggesting that a global understanding of the magnetic field system is necessary to explain what is observed in the corona. Calculations are presented which suggest that currents flowing up a flux rope return not in the immediate vicinity of the rope but rather in an alternative flux concentration located some distance away.

scholarly journals Photospheric magnetic field of an eroded-by-solar-wind coronal mass ejection

2016 ◽  
Vol 12 (S327) ◽  
pp. 67-70
Author(s):  
J. Palacios ◽  
C. Cid ◽  
E. Saiz ◽  
A. Guerrero
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Coronal Hole ◽  
Interplanetary Medium ◽  
Flux Rope ◽  
Magnetic Characteristics ◽  
Interplanetary Coronal Mass Ejection ◽  
Fast Wind ◽  
Mass Ejection

AbstractWe have investigated the case of a coronal mass ejection that was eroded by the fast wind of a coronal hole in the interplanetary medium. When a solar ejection takes place close to a coronal hole, the flux rope magnetic topology of the coronal mass ejection (CME) may become misshapen at 1 AU as a result of the interaction. Detailed analysis of this event reveals erosion of the interplanetary coronal mass ejection (ICME) magnetic field. In this communication, we study the photospheric magnetic roots of the coronal hole and the coronal mass ejection area with HMI/SDO magnetograms to define their magnetic characteristics.

The sheath region of April 2020 magnetic cloud and the associated energetic ions 

2021 ◽  
Author(s):  
Emilia Kilpua ◽  
Simon Good ◽  
Nina Dresing ◽  
Rami Vainio ◽  
Emma Davies ◽  
...  
Keyword(s):  
Flux Rope ◽  
Leading Edge ◽  
Heliospheric Current Sheet ◽  
Acceleration Process ◽  
Astrophysical Plasmas ◽  
Energetic Ions ◽  
Sheath Region ◽  
Open Questions ◽  
Mass Ejection

<p>Acceleration of energetic particles is a fundamental and ubiquitous mechanism in space and astrophysical plasmas. One of the open questions is the role of the sheath region behind the shock in the acceleration process. We analyze observations by Solar Orbiter, BepiColombo and the L1 spacecraft to explore the structure of a coronal mass ejection (CME)-driven sheath and its relation to enhancements of energetic ions that occurred on April 19-20, 2020. Our detailed analysis of the magnetic field, plasma and particle observations show that the enhancements were related to the Heliospheric Current Sheet crossings related to the reconnecting current sheets in the vicinity of the shock and a mini flux rope that was compressed at the leading edge of the CME ejecta. This study highlights the importance of smaller-scale sheath structures for the energization process. These structures likely formed already closer to the Sun and were swept and compressed from the upstream wind past the shock into the sheath. The upcoming observations by the recent missions (Solar Orbiter, Parker Solar Probe and BepiColombo) provide an excellent opportunity to explore further their role.  </p>

Theory and observations of switchbacks’ evolution in the solar wind

2021 ◽  
Author(s):  
Anna Tenerani ◽  
Marco Velli ◽  
Lorenzo Matteini
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Magnetic Field ◽  
Open Questions ◽  
Coronal Activity ◽  
Turbulent Heating ◽  
Field Lines ◽  
Radial Evolution ◽  
Field Correlation

<p>Alfvénic fluctuations represent the dominant contributions to turbulent fluctuations in the solar wind, especially, but not limited to, the fastest streams with velocity of the order of 600-700 km/s. Alfvénic fluctuations can contribute to solar wind heating and acceleration via wave pressure and turbulent heating. Observations show that such fluctuations are characterized by a nearly constant magnetic field amplitude, a condition which remains largely to be understood and that may be an indication of how fluctuations evolve and relax in the expanding solar wind. Interestingly, measurements from Parker Solar Probe have shown the ubiquitous and persistent presence of the so-called switchbacks. These are magnetic field lines which are strongly perturbed to the point that they produce local inversions of the radial magnetic field. The corresponding signature of switchbacks in the velocity field is that of local enhancements in the radial speed (or jets) that display the typical velocity-magnetic field correlation that characterizes Alfvén waves propagating away from the Sun. While there is not yet a general consensus on what is the origin of switchbacks and their connection to coronal activity, a first necessary step to answer these important questions is to understand how they evolve and how long they can persist in the solar wind. Here we investigate the evolution of switchbacks. We address how their evolution is affected by parametric instabilities and the possible role of expansion, by comparing models with the observed radial evolution of the fluctuations’ amplitude. We finally discuss what are the implications of our results for models of switchback generation and related open questions.</p>

Estimation of the spatial structure of a detached magnetic flux rope at Mars based on simultaneous MAVEN plasma and magnetic field observations

2015 ◽  
Vol 42 (21) ◽  
pp. 8933-8941 ◽  
Author(s):  
Takuya Hara ◽  
David L. Mitchell ◽  
James P. McFadden ◽  
Kanako Seki ◽  
David A. Brain ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Spatial Structure ◽  
Flux Rope ◽  
Field Observations ◽  
Magnetic Flux Rope

Evidence of an Erupting Magnetic Flux Rope: LASCO Coronal Mass Ejection of 1997 April 13

1997 ◽  
Vol 490 (2) ◽  
pp. L191-L194 ◽  
Author(s):  
J. Chen ◽  
R. A. Howard ◽  
G. E. Brueckner ◽  
R. Santoro ◽  
J. Krall ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Coronal Mass Ejection ◽  
Flux Rope ◽  
Magnetic Flux Rope ◽  
Mass Ejection
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