THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC MODELS OF TWISTED MULTITHREADED CORONAL LOOP OSCILLATIONS

2009 ◽  
Vol 694 (1) ◽  
pp. 502-511 ◽  
Author(s):  
L. Ofman
Keyword(s):  
Coronal Loop ◽  
Three Dimensional ◽  
Magnetohydrodynamic Models

scholarly journals A class of three-dimensional gyroviscous magnetohydrodynamic models

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
Manasvi Lingam ◽  
Philip J. Morrison ◽  
Alexander Wurm
Keyword(s):  
First Principles ◽  
Three Dimensional ◽  
Action Principle ◽  
Wide Range ◽  
Magnetohydrodynamic Models

A Hamiltonian and action principle formalism for deriving three-dimensional gyroviscous magnetohydrodynamic models is presented. The uniqueness of the approach in constructing the gyroviscous tensor from first principles and its ability to explain the origin of the gyromap and the gyroviscous terms are highlighted. The procedure allows for the specification of free functions, which can be used to generate a wide range of gyroviscous models. Through the process of reduction, the noncanonical Hamiltonian bracket is obtained and briefly analysed.

VERIFICATION OF CORONAL LOOP DIAGNOSTICS USING REALISTIC THREE-DIMENSIONAL HYDRODYNAMIC MODELS

2014 ◽  
Vol 795 (2) ◽  
pp. 138 ◽  
Author(s):  
Amy R. Winebarger ◽  
Roberto Lionello ◽  
Yung Mok ◽  
Jon A. Linker ◽  
Zoran Mikić
Keyword(s):  
Coronal Loop ◽  
Three Dimensional ◽  
Hydrodynamic Models

The Small-Scale Structure of Coronal Loops

1994 ◽  
Vol 144 ◽  
pp. 189-193
Author(s):  
M. A. Berger
Keyword(s):  
Equilibrium State ◽  
Coronal Loop ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Primary Source ◽  
Small Scale ◽  
Topological Complexity ◽  
Coronal Loops ◽  
Before And After ◽  
Dissipation Model

AbstractHow do we model coronal loops which contain a rich internal structure? Coronal loops usually lie close to the equilibrium state, but equilibrium fields are generally nonlinear, three-dimensional, and contain intense current layers. Nevertheless, it is important to study highly structured loops. Small reconnection events (microflares and nanoflares) which simplify the structure may be the primary source of heat in the closed corona. The magnetic energy released during a reconnection event can be estimated if one knows the equilibrium energy before and after the event. Furthermore, structured or tangled fields dissipate wave energy more efficiently than smooth fields. Here we present a method for studying tangled fields. Lower bounds can be placed on the energy of the equilibrium field, given a measure of the topological complexity known as the crossing number. These bounds provide an estimate of the energy generated in a coronal loop due to random photospheric motions. This calculation is used to estimate the heating rate in Parker’s topological dissipation model.

scholarly journals 3D Magnetic Reconnection

2010 ◽  
Vol 6 (S271) ◽  
pp. 227-238 ◽  
Author(s):  
Clare E. Parnell ◽  
Rhona C. Maclean ◽  
Andrew L. Haynes ◽  
Klaus Galsgaard
Keyword(s):  
Magnetic Reconnection ◽  
Energy State ◽  
Single Point ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Wide Range ◽  
Field Lines ◽  
Magnetohydrodynamic Models ◽  
The Magnetic Field

AbstractMagnetic reconnection is an important process that is prevalent in a wide range of astrophysical bodies. It is the mechanism that permits magnetic fields to relax to a lower energy state through the global restructuring of the magnetic field and is thus associated with a range of dynamic phenomena such as solar flares and CMEs. The characteristics of three-dimensional reconnection are reviewed revealing how much more diverse it is than reconnection in two dimensions. For instance, three-dimensional reconnection can occur both in the vicinity of null points, as well as in the absence of them. It occurs continuously and continually throughout a diffusion volume, as opposed to at a single point, as it does in two dimensions. This means that in three-dimensions field lines do not reconnect in pairs of lines making the visualisation and interpretation of three-dimensional reconnection difficult.By considering particular numerical 3D magnetohydrodynamic models of reconnection, we consider how magnetic reconnection can lead to complex magnetic topologies and current sheet formation. Indeed, it has been found that even simple interactions, such as the emergence of a flux tube, can naturally give rise to ‘turbulent-like’ reconnection regions.

A Three‐dimensional Dynamical Model of Current Sheet Formation in a Coronal Loop

2002 ◽  
Vol 578 (1) ◽  
pp. 573-589 ◽  
Author(s):  
D. W. Longcope ◽  
A. A. Van Ballegooijen
Keyword(s):  
Current Sheet ◽  
Coronal Loop ◽  
Three Dimensional ◽  
Dynamical Model

scholarly journals Coronal Loop Mapping to Infer the Best Magnetic Field Models for Active Region Prominences

2013 ◽  
Vol 8 (S300) ◽  
pp. 416-417
Author(s):  
G. Allen Gary ◽  
Qiang Hu ◽  
Jong Kwan Lee
Keyword(s):  
Magnetic Field ◽  
Coronal Loop ◽  
Field Model ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Magnetic Field Model ◽  
Free Parameters ◽  
Field Lines ◽  
Fitness Parameter ◽  
The Magnetic Field

AbstractThis article comments on the results of a new, rapid, and flexible manual method to map on-disk individual coronal loops of a two-dimensional EUV image into the three-dimensional coronal loops. The method by Gary, Hu, and Lee (2013) employs cubic Bézier splines to map coronal loops using only four free parameters per loop. A set of 2D splines for coronal loops is transformed to the best 3D pseudo-magnetic field lines for a particular coronal model. The results restrict the magnetic field models derived from extrapolations of magnetograms to those admissible and inadmissible via a fitness parameter. This method uses the minimization of the misalignment angles between the magnetic field model and the best set of 3D field lines that match a set of closed coronal loops. We comment on the implication of the fitness parameter in connection with the magnetic free energy and comment on extensions of our earlier work by considering the issues of employing open coronal loops or employing partial coronal loop.

scholarly journals Determining whether the squashing factor, Q, would be a good indicator of reconnection in a resistive MHD experiment devoid of null points

2020 ◽  
Vol 633 ◽  
pp. A92
Author(s):  
J. Reid ◽  
C. E. Parnell ◽  
A. W. Hood ◽  
P. K. Browning
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Coronal Loop ◽  
Ohmic Heating ◽  
Three Dimensional ◽  
Necessary And Sufficient Condition ◽  
Geometric Measure ◽  
Self Consistent ◽  
Necessary And Sufficient ◽  
The Magnetic Field

The squashing factor of a magnetic field, Q, is commonly used as an indicator of magnetic reconnection, but few studies seek to evaluate how reliable it is in comparison with other possible reconnection indicators. By using a full, self-consistent, three-dimensional, resistive magnetohydrodynamic experiment of interacting magnetic strands constituting a coronal loop, Q and several different quantities are determined. Each is then compared with the necessary and sufficient condition for reconnection, namely the integral along a field line of the component of the electric field parallel to the magnetic field. Among the reconnection indicators explored, we find the squashing factor less successful when compared with alternatives, such as Ohmic heating. In a reconnecting magnetic field devoid of null points, our work suggests that Q, being a geometric measure of the magnetic field, is not a reliable indicator of the onset or a diagnostic of the location of magnetic reconnection in some configurations.

scholarly journals From three-dimensional to quasi-two-dimensional: transient growth in magnetohydrodynamic duct flows

2018 ◽  
Vol 861 ◽  
pp. 382-406 ◽  
Author(s):  
Oliver G. W. Cassells ◽  
Tony Vo ◽  
Alban Pothérat ◽  
Gregory J. Sheard
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Layer Thickness ◽  
Hartmann Number ◽  
Three Dimensional ◽  
Transient Growth ◽  
Two Dimensional ◽  
Growth Mechanisms ◽  
Electrically Conducting ◽  
Magnetohydrodynamic Models

This study seeks to elucidate the linear transient growth mechanisms in a uniform duct with square cross-section applicable to flows of electrically conducting fluids under the influence of an external magnetic field. A particular focus is given to the question of whether at high magnetic fields purely two-dimensional mechanisms exist, and whether these can be described by a computationally inexpensive quasi-two-dimensional model. Two Reynolds numbers of $5000$ and $15\,000$ and an extensive range of Hartmann numbers $0\leqslant \mathit{Ha}\leqslant 800$ were investigated. Three broad regimes are identified in which optimal mode topology and non-modal growth mechanisms are distinct. These regimes, corresponding to low, moderate and high magnetic field strengths, are found to be governed by the independent parameters; Hartmann number, Reynolds number based on the Hartmann layer thickness $R_{H}$ and Reynolds number built upon the Shercliff layer thickness $R_{S}$, respectively. Transition between regimes respectively occurs at $\mathit{Ha}\approx 2$ and no lower than $R_{H}\approx 33.\dot{3}$. Notably for the high Hartmann number regime, quasi-two-dimensional magnetohydrodynamic models are shown to be excellent predictors of not only transient growth magnitudes, but also the fundamental growth mechanisms of linear disturbances. This paves the way for a precise analysis of transition to quasi-two-dimensional turbulence at much higher Hartmann numbers than is currently achievable.

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