scholarly journals Determining the dynamics and magnetic fields in He I 10830 Å during a solar filament eruption

2020 ◽  
Vol 640 ◽  
pp. A71 ◽  
Author(s):  
C. Kuckein ◽  
S. J. González Manrique ◽  
L. Kleint ◽  
A. Asensio Ramos
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Initial Conditions ◽  
Physical Conditions ◽  
Filament Eruption ◽  
Raster Scan ◽  
Solar Filament ◽  
Field Lines ◽  
Raster Scans ◽  
The Magnetic Field

Aims. We investigate the dynamics and magnetic properties of the plasma, including the line-of-sight velocity (LOS) and optical depth, as well as the vertical and horizontal magnetic fields, belonging to an erupted solar filament. Methods. The filament eruption was observed with the GREGOR Infrared Spectrograph at the 1.5-meter GREGOR telescope on July 3, 2016. We acquired three consecutive full-Stokes slit-spectropolarimetric scans in the He I 10830 Å spectral range. The Stokes I profiles were classified using the machine learning k-means algorithm and then inverted with different initial conditions using the HAZEL code. Results. The erupting-filament material presents the following physical conditions: (1) ubiquitous upward motions with peak LOS velocities of ∼73 km s−1; (2) predominant large horizontal components of the magnetic field, on average, in the range of 173−254 G, whereas the vertical components of the fields are much lower, on average between 39 and 58 G; (3) optical depths in the range of 0.7−1.1. The average azimuth orientation of the field lines between two consecutive raster scans (<2.5 min) remained constant. Conclusions. The analyzed filament eruption belongs to the fast rising phase, with total velocities of about 124 km s−1. The orientation of the magnetic field lines does not change from one raster scan to the other, indicating that the untwisting phase has not yet started. The untwisting appears to start about 15 min after the beginning of the filament eruption.

Magnetic Field Spectroheliograms from the San Fernando Observatory

1971 ◽  
Vol 43 ◽  
pp. 329-339 ◽  
Author(s):  
Dale Vrabec
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Spiral Structure ◽  
Longitudinal Component ◽  
Solar Telescope ◽  
Solar Magnetic Fields ◽  
San Fernando ◽  
Field Lines ◽  
The Magnetic Field ◽  
Field Network

Zeeman spectroheliograms of photospheric magnetic fields (longitudinal component) in the CaI 6102.7 Å line are being obtained with the new 61-cm vacuum solar telescope and spectroheliograph, using the Leighton technique. The structure of the magnetic field network appears identical to the bright photospheric network visible in the cores of many Fraunhofer lines and in CN spectroheliograms, with the exception that polarities are distinguished. This supports the evolving concept that solar magnetic fields outside of sunspots exist in small concentrations of essentially vertically oriented field, roughly clumped to form a network imbedded in the otherwise field-free photosphere. A timelapse spectroheliogram movie sequence spanning 6 hr revealed changes in the magnetic fields, including a systematic outward streaming of small magnetic knots of both polarities within annular areas surrounding several sunspots. The photospheric magnetic fields and a series of filtergrams taken at various wavelengths in the Hα profile starting in the far wing are intercompared in an effort to demonstrate that the dark strands of arch filament systems (AFS) and fibrils map magnetic field lines in the chromosphere. An example of an active region in which the magnetic fields assume a distinct spiral structure is presented.

scholarly journals Probing interstellar magnetic fields with Supernova remnants

2008 ◽  
Vol 4 (S259) ◽  
pp. 75-80 ◽  
Author(s):  
Roland Kothes ◽  
Jo-Anne Brown
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Field Configuration ◽  
Large Scale Magnetic Field ◽  
Rotation Measure ◽  
Field Lines ◽  
The Magnetic Field

AbstractAs Supernova remnants expand, their shock waves are freezing in and compressing the magnetic field lines they encounter; consequently we can use Supernova remnants as magnifying glasses for their ambient magnetic fields. We will describe a simple model to determine emission, polarization, and rotation measure characteristics of adiabatically expanding Supernova remnants and how we can exploit this model to gain information about the large scale magnetic field in our Galaxy. We will give two examples: The SNR DA530, which is located high above the Galactic plane, reveals information about the magnetic field in the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre of our Galaxy and reveals the most probable direction where the large-scale magnetic field is perpendicular to the line of sight. This may help to decide on the large-scale magnetic field configuration of our Galaxy. But more observations of SNRs are needed.

scholarly journals Structure of magnetic fields in spiral galaxies

2008 ◽  
Vol 4 (S259) ◽  
pp. 551-552
Author(s):  
Hanna Kotarba ◽  
H. Lesch ◽  
K. Dolag ◽  
T. Naab ◽  
P. H. Johansson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Homogeneous Field ◽  
Field Equations ◽  
The Galaxy ◽  
Induction Equation ◽  
Tight Connection ◽  
Field Lines ◽  
The Magnetic Field ◽  
Direct Implementation

AbstractWe present a set of global, self-consistentN-body/SPH simulations of the dynamic evolution of galactic discs with gas and including magnetic fields. We have implemented a description to follow the ideal induction equation in the SPH part of the codeVine. Results from a direct implementation of the field equations are compared to a representation by Euler potentials, which pose a ∇ ċB-free description, a constraint not fulfilled for the direct implementation. All simulations are compared to an implementation of magnetic fields in the codeGadget. Starting with a homogeneous field we find a tight connection of the magnetic field structure to the density pattern of the galaxy in our simulations, with the magnetic field lines being aligned with the developing spiral pattern of the gas. Our simulations clearly show the importance of non-axisymmetry of the dynamic pattern for the evolution of the magnetic field.

scholarly journals Measuring Magnetic Fields from Water Masers Associated with a Synchrotron Protostellar Jet

2017 ◽  
Vol 13 (S336) ◽  
pp. 215-218
Author(s):  
Ciriaco Goddi ◽  
Gabriele Surcis
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Zeeman Splitting ◽  
High Mass ◽  
Local Magnetic Field ◽  
Mass Star ◽  
Dominant Component ◽  
Field Lines ◽  
Water Masers ◽  
The Magnetic Field

AbstractThe Turner-Welch Object in the W3(OH) high-mass star forming complex drives a synchrotron jet, which is quite exceptional for a high-mass protostar, and is associated with a strongly polarized water maser source, W3(H2O), making it an optimal target to investigate the role of magnetic fields on the innermost scales of protostellar disk-jet systems. We report here full polarimetric VLBA observations of water masers. The linearly polarized emission from water masers provides clues on the orientation of the local magnetic field, while the measurement of the Zeeman splitting from circular polarization provides its strength. By combining the information on the measured orientation and strength of the magnetic field with the knowledge of the maser velocities, we infer that the magnetic field evolves from having a dominant component parallel to the outflow velocity in the pre-shock gas (with field strengths of the order of a few tens of mG), to being mainly dominated by the perpendicular component (of order of a few hundred of mG) in the post-shock gas where the water masers are excited. The general implication is that in the undisturbed (i.e. not-shocked) circumstellar gas, the flow velocities would follow closely the magnetic field lines, while in the shocked gas the magnetic field would be re-configured to be parallel to the shock front as a consequence of gas compression.

V. Heating and Dynamics of Chromosphere and Corona

1988 ◽  
Vol 20 (1) ◽  
pp. 100-102
Author(s):  
G.E. Brueckner
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Acoustic Waves ◽  
Convection Zone ◽  
Flux Tubes ◽  
Magnetic Structures ◽  
Convective Motions ◽  
Field Lines ◽  
The Magnetic Field

The crucial role of magnetic fields in any mechanism to heat the outer solar atmosphere has been generally accepted by all authors. However, there is still no agreement about the detailed function of the magnetic field. Heating mechanisms can be divided up into 4 classes: (I) The magnetic field plays a passive role as a suitable medium for the propagation of Alfvén waves from the convection zone into the corona (Ionson, 1984). (II) In closed magnetic structures the slow random shuffling of field lines by convective motions below the surface induces electric currents in the corona which heat it by Joule dissipation (Heyvaerts and Priest, 1984). (Ill) Emerging flux which is generated in the convection zone reacts with ionized material while magnetic field lines move through the chromosphere, transition zone and corona. Rapid field line annihilation, reconnection and drift currents result in heating and material ejection (Brueckner, 1987; Brueckner et al., 1987; Cook et al., 1987). (IV) Acoustic waves which could heat the corona can be guided by magnetic fields. Temperature distribution, wave motions and shock formation are highly dependent on the geometry of the flux tubes (Ulmschneider and Muchmore, 1986; Ulmschneider, Muchmore and Kalkofen, 1987).

scholarly journals Convective mechanism of amplification and structuring of magnetic fields

2012 ◽  
Vol 8 (S294) ◽  
pp. 137-142
Author(s):  
A. V. Getling ◽  
V. V. Kolmychkov ◽  
O. S. Mazhorova
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Incompressible Fluid ◽  
Spatial Scales ◽  
Fluid Motion ◽  
Horizontal Layer ◽  
Field Lines ◽  
The Magnetic Field ◽  
Initial Magnetic Field ◽  
Peripheral Regions

AbstractMagnetoconvection in a horizontal layer of incompressible fluid is simulated numerically. The initial magnetic field is assumed to be uniform and horizontal. The interaction of quasi-ordered cellular convection with the magnetic field is shown to be able to produce bipolar (and also diverse more complex) configurations of a substantially amplified magnetic field. The operation of this mechanism, which can be regarded as a modification of the mechanism suggested by Tverskoi (1966), is controlled by the very topology of the cellular flow, should be manifest on various spatial scales, and does not require strong initial fields. Magnetic configurations develop both in the central parts of convection cells, where circulatory fluid motion “winds” magnetic field lines, and in the network formed by their peripheral regions due to the “sweeping” of magnetic field lines.

scholarly journals Hall Effect in Neutron Star Crusts

2013 ◽  
Vol 9 (S302) ◽  
pp. 415-418
Author(s):  
K. N. Gourgouliatos ◽  
A. Cumming
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Large Scale ◽  
Initial Conditions ◽  
Free Electrons ◽  
Solid Crystal ◽  
Field Lines ◽  
Evolutionary Paths ◽  
The Magnetic Field ◽  
Turbulent Cascade

AbstractThe crust of Neutron Stars can be approximated by a highly conducting solid crystal lattice. The evolution of the magnetic field in the crust is mediated through Hall effect, namely the electric current is carried by the free electrons of the lattice and the magnetic field lines are advected by the electron fluid. Here, we present the results of a time-dependent evolution code which shows the effect Hall drift has in the large-scale evolution of the magnetic field. In particular we link analytical predictions with simulation results. We find that there are two basic evolutionary paths, depending on the initial conditions compared to Hall equilibrium. We also show the effect axial symmetry combined with density gradient have on suppressing turbulent cascade.

scholarly journals Striations, integrals, hourglasses, and collapse – thermal instability driven magnetic simulations of molecular clouds

2020 ◽  
Vol 500 (3) ◽  
pp. 2831-2849
Author(s):  
C J Wareing ◽  
J M Pittard ◽  
S A E G Falle
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Adaptive Mesh Refinement ◽  
Thermal Instability ◽  
Initial Conditions ◽  
Power Spectra ◽  
Adaptive Mesh ◽  
Spherical Cloud ◽  
Field Lines ◽  
Self Gravity

ABSTRACT The MHD version of the adaptive mesh refinement (AMR) code, MG, has been employed to study the interaction of thermal instability, magnetic fields, and gravity through 3D simulations of the formation of collapsing cold clumps on the scale of a few parsecs, inside a larger molecular cloud. The diffuse atomic initial condition consists of a stationary, thermally unstable, spherical cloud in pressure equilibrium with lower density surroundings and threaded by a uniform magnetic field. This cloud was seeded with 10 per cent density perturbations at the finest initial grid level around n = 1.1 cm−3 and evolved with self-gravity included from the outset. Several cloud diameters were considered (100, 200, and 400 pc) equating to several cloud masses (17 000, 136 000, and 1.1 × 106 M⊙). Low-density magnetic-field-aligned striations were observed as the clouds collapse along the field lines into disc-like structures. The induced flow along field lines leads to oscillations of the sheet about the gravitational minimum and an integral-shaped appearance. When magnetically supercritical, the clouds then collapse and generate hourglass magnetic field configurations with strongly intensified magnetic fields, reproducing observational behaviour. Resimulation of a region of the highest mass cloud at higher resolution forms gravitationally bound collapsing clumps within the sheet that contain clump-frame supersonic (M ∼ 5) and super-Alfvénic (MA ∼ 4) velocities. Observationally realistic density and velocity power spectra of the cloud and densest clump are obtained. Future work will use these realistic initial conditions to study individual star and cluster feedback.

scholarly journals Particle Acceleration in the Process of Eruptive Opening and Reconnection of Magnetic Fields

1980 ◽  
Vol 91 ◽  
pp. 217-221 ◽  
Author(s):  
Z. Švestka ◽  
S. F. Martin ◽  
R. A. Kopp
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Particle Acceleration ◽  
Magnetic Fields ◽  
Magnetic Loop ◽  
Coronal Loops ◽  
X Rays ◽  
Flare Loops ◽  
Field Lines ◽  
The Magnetic Field

In a series of papers on the flare of 29 July 1973 (Nolte et al., 1979; Martin, 1979; Švestka et al., 1979) it has been shown that Hα “post-flare” loops are the cooled aftermath of previously hot coronal loops which were visible in x-rays in the same position earlier in the flare. Kopp and Pneuman (1976) have proposed that these post-flare loops are formed by a process of successive magnetic field reconnections of previously distended magnetic field lines as illustrated in Figure 1. Each successive reconnection of the magnetic field yields a closed magnetic loop that forms above and concentric with previously formed loops. A shock wave created during each sudden reconnection travels down both legs of each loop and provides energy for ionizing chromospheric mass at the footpoints of the loop. Subsequent condensation of the ionized mass at the tops of the loops renders them visible as this mass falls to the chromosphere.

scholarly journals Magnetic fields in massive spirals: The role of feedback and initial conditions

2018 ◽  
Vol 619 ◽  
pp. L5 ◽  
Author(s):  
Evangelia Ntormousi
Keyword(s):  
Magnetic Field ◽  
Velocity Field ◽  
Magnetic Fields ◽  
Field Component ◽  
Initial Conditions ◽  
Magnetic Field Component ◽  
Stellar Feedback ◽  
Random Magnetic Field ◽  
Supernova Feedback ◽  
The Magnetic Field

Context. Magnetic fields play a very important role in the evolution of galaxies through their direct impact on star formation and stellar feedback-induced turbulence. However, their co-evolution with these processes has still not been thoroughly investigated, and the possible effect of the initial conditions is largely unknown. Aims. This Letter presents the first results from a series of high-resolution numerical models, aimed at deciphering the effect of the initial conditions and of stellar feedback on the evolution of the galactic magnetic field in isolated Milky Way-like galaxies. Methods. The models start with an ordered magnetic field of varying strength, either poloidal or toroidal, and are evolved with and without supernova feedback. They include a dark matter halo, a stellar and a gaseous disk, as well as the appropriate cooling and heating processes for the interstellar medium. Results. Independently of the initial conditions, the galaxies develop a turbulent velocity field and a random magnetic field component in under 15 Myr. Supernova feedback is extremely efficient in building a random magnetic field component up to large galactic heights. However, a random magnetic field emerges even in runs without feedback, which points to an inherent instability of the ordered component. Conclusions. Supernova feedback greatly affects the velocity field of the galaxy up to large galactic heights, and helps restructure the magnetic field up to 10 kpc above the disk, independently of the initial magnetic field morphology. On the other hand, the initial morphology of the magnetic field can accelerate the development of a random component at large heights. These effects have important implications for the study of the magnetic field evolution in galaxy simulations.

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