scholarly journals Evolution of auroral substorm as viewed from MHD simulations: dynamics, energy transfer and energy conversion

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Yusuke Ebihara ◽  
Takashi Tanaka
Keyword(s):  
Energy Transfer ◽  
Large Scale ◽  
A Priori ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
The Earth ◽  
Auroral Substorm ◽  
Transient Disturbances ◽  
Global Mhd Simulation

AbstractAn auroral substorm is a visual manifestation of large-scale, transient disturbances taking place in space surrounding the Earth, and is one of the central issues in the space plasma physics. While a number of studies have been conducted, a unified picture of the overall evolution of the auroral substorm has not been drawn. This paper is aimed to overview the recently obtained results of global magnetohydrodynamics (MHD) simulations in a context of a priori presence of anomalous resistivity leading to magnetic reconnection, and to illuminate what the global MHD simulation can sufficiently reproduce the auroral transients during the auroral substorm. Some auroral transients are found to be seamlessly reproduced by the MHD simulation, including complicated auroral structures moving equatorward during the growth phase, auroral brightening starting to appear near the equatorward border of the preexisting auroral arc, and an auroral surge traveling westward. Possible energy transfer and conversion from the solar wind to the Earth are also overviewed on the basis of the MHD simulation. At least, 4 dynamo regions appear sequentially in the course of the development of the auroral substorm. Although the MHD simulation reproduces some transients, further studies are needed to investigate the role of kinetic processes.

scholarly journals MHD simulations of ram pressure stripping of disk galaxies

2015 ◽  
Vol 11 (S319) ◽  
pp. 143-143
Author(s):  
Mariana Ramos-Martínez ◽  
Gilberto C. Gómez
Keyword(s):  
Wind Tunnel ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Galactic Disk ◽  
Disk Galaxies ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Ram Pressure ◽  
3D Mhd Simulation

AbstractThe removal of ISM of disk galaxies through ram pressure stripping (RPS) has been extensively studied in numerous simulations (see Roediger 2009 and references therein). The models show that RPS has a significant impact on galaxy evolution (truncation of the ISM will lead to a decrease in star formation and a change in galaxy color). Nevertheless, the role of magnetic fields (MFs) on the dynamics of the gas in this process has not been sufficiently studied, although the influence of the MFs on the large scale structure is well established. This motivated us to perform a 3D MHD simulation of a disk galaxy with an isothermal, non-self gravitating and magnetized gaseous disk in equilibrium with a galaxy potential (Allen & Santillán, 1991). We model RPS on the galactic disk under the wind-tunnel approximation with the use of the RAMSES code (Teyssier, 2002) in order to understand the effects of MFs in RPS.

scholarly journals A general Cluster data and global MHD simulation comparison

2008 ◽  
Vol 26 (11) ◽  
pp. 3411-3428 ◽  
Author(s):  
P. Daum ◽  
M. H. Denton ◽  
J. A. Wild ◽  
M. G. G. T. Taylor ◽  
J. Šafránková ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Mhd Simulation ◽  
Global Context ◽  
Cluster Data ◽  
Verification Methods ◽  
Modelling Studies ◽  
Global Mhd Simulation ◽  
The Many

Abstract. Among the many challenges facing the space weather modelling community today, is the need for validation and verification methods of the numerical models available describing the complex nonlinear Sun-Earth system. Magnetohydrodynamic (MHD) models represent the latest numerical models of this environment and have the unique ability to span the enormous distances present in the magnetosphere, from several hundred kilometres to several thousand kilometres above the Earth's surface. This makes it especially difficult to develop verification and validation methods which posses the same range spans as the models. In this paper we present a first general large-scale comparison between four years (2001–2004) worth of in situ Cluster plasma observations and the corresponding simulated predictions from the coupled Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) MHD code. The comparison between the in situ measurements and the model predictions reveals that by systematically constraining the MHD model inflow boundary conditions a good correlation between the in situ observations and the modeled data can be found. These results have an implication for modelling studies addressing also smaller scale features of the magnetosphere. The global MHD simulation can therefore be used to place localised satellite and/or ground-based observations into a global context and fill the gaps left by measurements.

scholarly journals Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study

2004 ◽  
Vol 22 (3) ◽  
pp. 951-970 ◽  
Author(s):  
A. Kullen ◽  
P. Janhunen
Keyword(s):  
Magnetic Field ◽  
Simulation Study ◽  
Large Scale ◽  
Detailed Examination ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Sign Change ◽  
Auroral Arcs ◽  
Good Agreement ◽  
Imf Clock Angle

Abstract. We investigate with the help of a magnetohydrodynamic (MHD) model how the large-scale topology of the magnetosphere develops for a constant interplanetary magnetic field (IMF) with different IMF clock angles and for an IMF By sign change during northward IMF. A detailed examination of the topological changes in the tail and the ionosphere for different IMF conditions shows a good agreement with observational results. The MHD simulations for different constant IMF clock angle cases show the expected field-line bending and tail twisting for nonzero IMF By. The tail becomes longer and at its tailward end stronger twisted for IMF Bz>∣By∣ than for IMF Bz

scholarly journals MHD simulations of star-disk magnetospheres and the formation of outflows and jets

2007 ◽  
Vol 3 (S243) ◽  
pp. 265-276
Author(s):  
Christian Fendt
Keyword(s):  
Numerical Simulation ◽  
Stellar Wind ◽  
Large Scale ◽  
Disk Surface ◽  
Time Dependent ◽  
Mhd Simulations ◽  
Tremendous Progress ◽  
Stellar Magnetospheres ◽  
Scale Evolution

AbstractIn this review the recent development concerning the large-scale evolution of stellar magnetospheres in interaction with the accretion disk is discussed. I put emphasis on the generation of outflows and jets from the disk and/or the star. In fact, tremendous progress has occurred over the last decade in the numerical simulation of the star-disk interaction. The role of numerical simulations is essential in this area because the processes involved are complex, strongly interrelated, and often highly time-dependent. Recent MHD simulations suggest that outflows launched from a very concentrated region tend to be un-collimated. I present preliminary results of simulations of large-scale star-disk magnetospheres loaded with matter from the stellar, resp. the disk surface demonstrating how a disk jet collimates the wind from the star and also how the stellar wind lowers the collimation degree of the disk outflow.

scholarly journals Flare particle acceleration in the interaction of twisted coronal flux ropes

2018 ◽  
Vol 611 ◽  
pp. A40 ◽  
Author(s):  
J. Threlfall ◽  
A. W. Hood ◽  
P. K. Browning
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Uniform Background ◽  
Energy Gains ◽  
Particle Behaviour

Aim. The aim of this work is to investigate and characterise non-thermal particle behaviour in a three-dimensional (3D) magnetohydrodynamical (MHD) model of unstable multi-threaded flaring coronal loops.Methods. We have used a numerical scheme which solves the relativistic guiding centre approximation to study the motion of electrons and protons. The scheme uses snapshots from high resolution numerical MHD simulations of coronal loops containing two threads, where a single thread becomes unstable and (in one case) destabilises and merges with an additional thread.Results. The particle responses to the reconnection and fragmentation in MHD simulations of two loop threads are examined in detail. We illustrate the role played by uniform background resistivity and distinguish this from the role of anomalous resistivity using orbits in an MHD simulation where only one thread becomes unstable without destabilising further loop threads. We examine the (scalable) orbit energy gains and final positions recovered at different stages of a second MHD simulation wherein a secondary loop thread is destabilised by (and merges with) the first thread. We compare these results with other theoretical particle acceleration models in the context of observed energetic particle populations during solar flares.

scholarly journals Geodynamic modeling of the process of formation and evolution of lithospheric structures: experience of Schmidt institute of physics of the earth RAS

2019 ◽  
pp. 122-133
Author(s):  
V. O. Mikhailov ◽  
E. P. Timoshkina
Keyword(s):  
Large Scale ◽  
Sedimentary Basins ◽  
Geophysical Data ◽  
Small Scale ◽  
Tectonic Structures ◽  
The Earth ◽  
Basin Formation ◽  
Formation And Evolution ◽  
Geodynamic Models

Key results of numerical geodynamic modeling of the structures of the lithosphere at the Institute of Physics of the Earth of the Russian Academy of Sciences are presented. Even in the very first models, the aim of these studies was to describe the time evolution of the boundaries of the layers composing the geological structures which is required for correlating the modeling results to the geological and geophysical data. In 1983, the equation of motion for the upper boundary of the model was complemented by the allowance of sedimentation and erosion. This equation provided the basis for building the geodynamic models of the formation of various types of sedimentary basins and made it possible to mathematically analyze the problem of estimating the rates of paleotectonic movements from thickness, age, and facies composition of sedimentary layers. New data on the formation and evolution processes of large-scale tectonic structures are obtained in the model of a rheologically stratified Earth’s boundary layer, asymptotically linked to mantle convection model. In particular, the role of the small-scale convection in the formation of lithospheric structures in the tectonic settings of extension and compression has been explored. The numerical results clearly demonstrate the key role of the small-scale asthenospheric convection in sedimentary basin formation (post-rift, on passive continental margins, in foredeep basins). The constructed models served as the basis for interpretation of heterogeneous geological and geophysical data in the context of geodynamic models. The examples of statement of inverse problems are presented and the relevant bibliography is provided.

The role of strain dependent rheology on formation of divergent plate boundaries

2020 ◽  
Author(s):  
Martina Ulvrova ◽  
Taras Gerya
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Strike Slip ◽  
Plate Boundaries ◽  
The Earth ◽  
Cartesian Geometry ◽  
Formation And Evolution ◽  
Narrow Plate ◽  
Strain Dependent

<p>Surface of the Earth is divided into distinct plates that move relative to each other. However, formation and evolution of new plate boundaries is still challenging to numerically produce and predict. In particular, regional lithospheric models as well as large scale convection models lack realistic strike slip plate boundaries that would arise self-consistently in such models. Here, we investigate the role of different rheologies on the inception and dynamic evolution of the new divergent plate boundaries and their offset by strike-slip faulting. We compare visco-plastic rheology and strain dependent rheology and their capacity to localise deformation into narrow plate limits. We use high-resolution 3D thermo-mechanical numerical models in  cartesian geometry to infer the conditions under which realistic divergent plate boundaries develop.</p>

scholarly journals Three-dimensional flow near a reconnection site at the dayside magnetopause: analytical solutions coupled with MHD simulations

2007 ◽  
Vol 73 (6) ◽  
pp. 811-819 ◽  
Author(s):  
LARS G. WESTERBERG ◽  
J. VEDIN ◽  
A. EKENBÄCK ◽  
H. O. ÅKERSTEDT
Keyword(s):  
Plasma Flow ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Three Dimensional Flow ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Dayside Magnetopause ◽  
Global Mhd Simulation ◽  
Reconnection Site

AbstractWe present a coupling between an analytical three-dimensional model covering the plasma flow behaviour through the magnetopause transition layer near a reconnection site, with results from a global MHD simulation describing the plasma flow in the magnetosheath. The structure of the plasma flow near a reconnection site at the dayside terrestrial magnetopause is investigated, together with the development of the magnetopause transition region.

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