scholarly journals An optimization principle for computing stationary MHD equilibria with solar wind flow

2020 ◽  
Author(s):  
Thomas Wiegelmann ◽  
Thomas Neukirch ◽  
Dieter Nickeler ◽  
Iulia Chifu
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Magnetic Field ◽  
Field Vector ◽  
Source Surface ◽  
Solar Chromosphere ◽  
Wind Flow ◽  
Solar Wind Flow ◽  
Nonlinear Force ◽  
The Magnetic Field

<p>Knowledge about the magnetic field and plasma environment is important<br>for almost all physical processes in the solar atmosphere. Precise<br>measurements of the magnetic field vector are done routinely only in<br>the photosphere, e.g. by SDO/HMI. These measurements are used as<br>boundary condition for modelling the solar chromosphere and corona,<br>whereas some model assumptions have to be made. In the low-plasma-beta<br>corona the Lorentz-force vanishes and the magnetic field<br>is reconstructed with a nonlinear force-free model. In the mixed-beta<br>chromosphere plasma forces have to be taken into account with the<br>help of a magnetostatic model. And finally for modelling the global<br>corona far beyond the source surface the solar wind flow has to<br>be incorporated within a stationary MHD model.<br>To do so, we generalize a nonlinear force-free and magneto-static optimization<br>code by the inclusion of a field aligned compressible plasma flow.<br>Applications are the implementation of the solar wind on<br>global scale. This allows to reconstruct the coronal magnetic field further<br>outwards than with potential field, nonlinear force-free and magneto-static models.<br>This way the model might help in future to provide the magnetic connectivity<br>for joint observations of remote sensing and in-situ instruments on Solar<br>Orbiter and Parker Solar Probe.</p>

Investigation of the magnetic field between the shock wave and the obstacle in the solar wind flow around a planet

1981 ◽  
Vol 1 (1) ◽  
pp. 101-104
Author(s):  
V.B. Boranov ◽  
E.G. Eroshenko ◽  
M.D. Kartalev ◽  
I.P. Mastikov
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Solar Wind ◽  
Wind Flow ◽  
Solar Wind Flow ◽  
The Magnetic Field

Waves in the magnetic field and solar wind flow outside the bow shock at comet P/Halley

1988 ◽  
pp. 47-54 ◽  
Author(s):  
A. Johnstone ◽  
K. Glassmeier ◽  
M. Acuna ◽  
H. Borg ◽  
D. Bryant ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Bow Shock ◽  
Wind Flow ◽  
Solar Wind Flow ◽  
The Magnetic Field

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Global coronal and heliospheric magnetic field modelling for Solar Orbiter

2021 ◽  
Author(s):  
Thomas Wiegelmann ◽  
Thomas Neukirch ◽  
Iulia Chifu ◽  
Bernd Inhester
Keyword(s):  
Magnetic Field ◽  
Solar Rotation ◽  
Coronal Magnetic Field ◽  
Important Research ◽  
Parker Spiral ◽  
Important Research Topic ◽  
Mhd Equilibria ◽  
Solar Wind Flow ◽  
Nonlinear Force

<p>Computing the solar coronal magnetic field and plasma<br>environment is an important research topic on it's own right<br>and also important for space missions like Solar Orbiter to<br>guide the analysis of remote sensing and in-situ instruments.<br>In the inner solar corona plasma forces can be neglected and<br>the field is modelled under the assumption of a vanishing<br>Lorentz-force. Further outwards (above about two solar radii)<br>plasma forces and the solar wind flow has to be considered.<br>Finally in the heliosphere one has to consider that the Sun<br>is rotating and the well known Parker-spiral forms.<br>We have developed codes based on optimization principles<br>to solve nonlinear force-free, magneto-hydro-static and<br>stationary MHD-equilibria. In the present work we want to<br>extend these methods by taking the solar rotation into account.</p>

scholarly journals Nonlinear force-free modeling of magnetic fields in flare-productive active regions

2015 ◽  
Vol 11 (S320) ◽  
pp. 167-174
Author(s):  
M. S. Wheatland ◽  
S. A. Gilchrist
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Boundary Data ◽  
Numerical Solutions ◽  
Free Field ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Nonlinear Force ◽  
The Magnetic Field ◽  
Force Free Field

AbstractWe review nonlinear force-free field (NLFFF) modeling of magnetic fields in active regions. The NLFFF model (in which the electric current density is parallel to the magnetic field) is often adopted to describe the coronal magnetic field, and numerical solutions to the model are constructed based on photospheric vector magnetogram boundary data. Comparative tests of NLFFF codes on sets of boundary data have revealed significant problems, in particular associated with the inconsistency of the model and the data. Nevertheless NLFFF modeling is often applied, in particular to flare-productive active regions. We examine the results, and discuss their reliability.

scholarly journals An integrated data-driven solar wind - CME numerical framework for space weather forecasting

2020 ◽  
Author(s):  
Nishant M. Narechania ◽  
Ljubomir Nikolic ◽  
Lucie Freret ◽  
Hans De Sterck ◽  
Clinton P. T. Groth
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Space Weather ◽  
Weather Forecasting ◽  
Coronal Magnetic Field ◽  
Data Driven ◽  
Source Surface ◽  
Field Source ◽  
Space Weather Forecasting ◽  
Semi Empirical

The development of numerical models and tools which have operational space weather potential is an increasingly important area of research. This study presents recent Canadian efforts toward the development of a numerical framework for Sun-to-Earth simulations of solar wind disturbances. This modular three-dimensional (3D) simulation framework is based on a semi-empirical data-driven approach to describe the solar corona and an MHD-based description of the heliosphere. In the present configuration, the semi-empirical component uses the Potential Field Source Surface (PFSS) and Schatten Current Sheet (SCS) models to derive the coronal magnetic field based on observed magnetogram data. Using empirical relations, solar wind properties are associated with this coronal magnetic field. Together with a Coronal Mass Ejection (CME) model, this provides inner boundary conditions for a global MHD model which is used to describe interplanetary propagation of the solar wind and CMEs. The proposed MHD numerical approach makes use of advanced numerical techniques. The 3D MHD code employs a finite-volume discretization procedure with limited piecewise linear reconstruction to solve the governing partial-differential equations. The equations are solved on a body-fitted hexahedral multi-block cubed-sphere mesh and an efficient iterative Newton method is used for time-invariant simulations and an explicit time-marching scheme is applied for unsteady cases. Additionally, an efficient anisotropic block-based refinement technique provides significant reductions in the size of the computational mesh by locally refining the grid in selected directions as dictated by the flow physics. The capabilities of the framework for accurately capturing solar wind structures and forecasting solar wind properties at Earth are demonstrated. Furthermore, a comparison with previously reported results and future space weather forecasting challenges are discussed.

scholarly journals On the Geoeffectiveness Structure of Solar Wind-Magnetosphere Coupling Functions during Intense Storms

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
B. Olufemi Adebesin ◽  
S. Oluwole Ikubanni ◽  
J. Stephen Kayode
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Cloud ◽  
Recovery Phase ◽  
Flow Speed ◽  
Event Correlation ◽  
Phase Duration ◽  
Event Identification ◽  
Solar Wind Flow ◽  
The Magnetic Field

The geoeffectiveness of some coupling functions for the Solar Wind-Magnetosphere Interaction had been studied. 58 storms with peak Dst < −100 nT were used. The result showed that the interplanetary magnetic field Bz appeared to be more relevant with the magnetic field B (which agreed with previous results). However, both the V (solar wind flow speed) and Bz factors in the interplanetary dawn-dusk electric field (V×Bz) are effective in the generation of very intense storms (peak Dst < −250 nT) while “intense” storms (−250 nT ≤ peak Dst < −100 nT) are mostly enhanced by the Bz factor alone (in most cases). The southward Bz duration BT seems to be more relevant for Dst < −250 nT class of storms and invariably determines the recovery phase duration. Most of the storms were observed to occur at midnight hours (i.e., 2100–0400 UT), having a 41.2% incidence rate, with high frequency between 2300 UT and 0000 UT. 62% of the events were generated as a result of Magnetic Cloud (MC), while 38% were generated by complex ejecta. The B-Bz relation for the magnetic cloud attained a correlation coefficient of 0.8922, while it is 0.7608 for the latter. Conclusively, Bz appears to be the most geoeffective factor, and geoeffectiveness should be a factor that depends on methods of event identification and classification as well as the direction of event correlation.

scholarly journals Global Coronal Equilibria with Solar Wind Outflow

2021 ◽  
Vol 923 (1) ◽  
pp. 57
Author(s):  
Oliver E. K. Rice ◽  
Anthony R. Yeates
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Potential Field ◽  
Field Model ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Radial Magnetic Field ◽  
Similar Time ◽  
Magnetic Field Model ◽  
Magnetohydrodynamic Simulations

Abstract Given a known radial magnetic field distribution on the Sun’s photospheric surface, there exist well-established methods for computing a potential magnetic field in the corona above. Such potential fields are routinely used as input to solar wind models, and to initialize magneto-frictional or full magnetohydrodynamic simulations of the coronal and heliospheric magnetic fields. We describe an improved magnetic field model that calculates a magneto-frictional equilibrium with an imposed solar wind profile (which can be Parker’s solar wind solution, or any reasonable equivalent). These “outflow fields” appear to approximate the real coronal magnetic field more closely than a potential field, take a similar time to compute, and avoid the need to impose an artificial source surface. Thus they provide a practical alternative to the potential field model for initializing time-evolving simulations or modeling the heliospheric magnetic field. We give an open-source Python implementation in spherical coordinates and apply the model to data from solar cycle 24. The outflow tends to increase the open magnetic flux compared to the potential field model, reducing the well-known discrepancy with in situ observations.

scholarly journals MHD effects of the solar wind flow around planets

2000 ◽  
Vol 7 (3/4) ◽  
pp. 201-210 ◽  
Author(s):  
H. K. Biernat ◽  
N. V. Erkaev ◽  
C. J. Farrugia ◽  
D. F. Vogl ◽  
W. Schaffenberger
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Mach Number ◽  
Boundary Conditions ◽  
Wind Flow ◽  
Magnetic Shear ◽  
Thermal Anisotropy ◽  
Terrestrial Magnetosphere ◽  
Solar Wind Flow

Abstract. The study of the interaction of the solar wind with magnetized and unmagnetized planets forms a central topic of space research. Focussing on planetary magnetosheaths, we review some major developments in this field. Magnetosheath structures depend crucially on the orientation of the interplanetary magnetic field, the solar wind Alfvén Mach number, the shape of the obstacle (axisymmetric/non-axisymmetric, etc.), the boundary conditions at the magnetopause (low/high magnetic shear), and the degree of thermal anisotropy of the plasma. We illustrate the cases of Earth, Jupiter and Venus. The terrestrial magnetosphere is axisymmetric and has been probed in-situ by many spacecraft. Jupiter's magnetosphere is highly non-axisymmetric. Furthermore, we study magnetohydrodynamic effects in the Venus magnetosheath.

Three-dimensional reconstruction of an expanding shock associated with a Solar particle event

2021 ◽  
Author(s):  
Federica Frassati ◽  
Monica Laurenza ◽  
Alessandro Bemporad ◽  
Matthew J. West ◽  
Salvatore Mancuso ◽  
...  
Keyword(s):  
Magnetic Field ◽  
3D Reconstruction ◽  
Ultra Violet ◽  
Coronal Magnetic Field ◽  
Release Time ◽  
Shock Acceleration ◽  
Source Surface ◽  
Type Ii ◽  
Field Source ◽  
The Magnetic Field

&lt;p&gt;&lt;span&gt;On 2013 June 21st an eruption occurred in the active region NOAA 1177 (14S73E), &lt;/span&gt;&lt;span&gt;giving rise to&lt;/span&gt; &lt;span&gt;a M2.9 class flare starting at 02:30 UT, a fast partial halo coronal mass ejection (CME), and a type II radio burst. The concomitant emission of solar energetic particles (SEPs) produced a significant increase in the proton fluxes measured by LET and HET aboard STEREO-B. By using stereoscopic observations in extreme ultra violet (EUV) and white light (WL) spectral intervals, we performed a 3D reconstruction of the expanding front by processing SDO/AIA, STEREO/EUVI, COR1 and COR2, and SOHO/LASCO data assuming a spheroidal model. By using the 3D reconstruction, we estimated the temporal evolution of &amp;#952;&lt;/span&gt;&lt;span&gt;&lt;sub&gt;Bn,&lt;/sub&gt;&lt;/span&gt;&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;span&gt;i.e.,&lt;/span&gt; &lt;span&gt;the angle between the normal to the expanding front and the coronal magnetic field computed by the Potential-Field Source-Surface (PFSS) approximation, within 2.5 R&lt;/span&gt;&lt;span&gt;&lt;sub&gt;&amp;#664;&lt;/sub&gt;&lt;/span&gt;&lt;span&gt;.&amp;#160;The front &lt;/span&gt;&lt;span&gt;of the CME&lt;/span&gt;&lt;span&gt;was found to be quasi-parallel to the magnetic field almost everywhere&lt;/span&gt;&lt;span&gt;&lt;sub&gt;.&lt;/sub&gt;&lt;/span&gt;&lt;span&gt;&amp;#160;Above 2.5 R&lt;/span&gt;&lt;span&gt;&lt;sub&gt;&amp;#664;&lt;/sub&gt;&lt;/span&gt;&lt;span&gt;, where the front was identified as a shock, we projected the 3D expanding surface &lt;/span&gt;&lt;span&gt;reconstructed for &lt;/span&gt;&lt;span&gt;different times on the ecliptic plane and&lt;/span&gt;&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;span&gt;we calculated the &amp;#952;&lt;/span&gt;&lt;span&gt;&lt;sub&gt;Bn&amp;#160;&lt;/sub&gt;&lt;/span&gt;&lt;span&gt;between the normal to the front and Parker spiral arms. In this case the shock was almost perpendicular to the magnetic field (quasi-parallel shock).&amp;#160;During the expansion the region located between the nose and the eastern flank of the shock was magnetically connected with ST-B in agreement with the significant SEP flux measured on-board this spacecraft.&lt;/span&gt; &lt;span&gt;W&lt;/span&gt;&lt;span&gt;hile&lt;/span&gt; &lt;span&gt;the shock was only marginally connected with ST-A and GOES-15. &lt;/span&gt;&lt;span&gt;T&lt;/span&gt;&lt;span&gt;he SEP release time was estimated to be 10 minutes after the Type II onset, when the shock front was already above 2.5 R&lt;/span&gt;&lt;span&gt;&lt;sub&gt;&amp;#664;&lt;/sub&gt;&lt;/span&gt;&lt;span&gt;&amp;#160;with a quasi-parallel configuration. Our results are discussed in the framework of the shock acceleration scenario, even if quasi-parallel shocks are expected to have a reduced acceleration efficiency.&lt;/span&gt;&lt;/p&gt;

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