Modelling the evolution of CMEs and their shocks through different solar wind structures

The evolution of coronal mass ejections (CMEs) as they travel away from the Sun is one of the major issues in heliophysics and space weather. After erupting, CMEs propagate outwards through the background solar wind flow, which in turn may significantly affect CME evolution by means of e.g. acceleration, deflection, and/or rotation. In order to determine to which extent the ambient wind can alter the speed, trajectory, and orientation of a CME, we run a series of 3D magnetohydrodynamics simulations (using the coupled solar&#8211;heliospheric WSA&#8211;Enlil model) to conduct a multi-vantage point study of the radial and longitudinal evolution of CME structures as they propagate up to Earth&#8217;s (1 AU) and Mars&#8217; (1.5 AU) orbits. We explore a broad range of input CME parameters (initial radial speed, angular width) and ambient solar wind conditions (slow versus fast wind) to investigate the different evolutionary behaviours of CMEs and their driven shocks and sheath regions. To study the radial and longitudinal evolution for the modelled CME ejecta and shock events, we examine the resulting magnetic field and plasma time series at different heliocentric distances (0.5 AU, 1 AU, and 1.5 AU) and heliolongitudes (in 30&#176; increments). This work will help establish a set of expected CME behaviours at Earth&#8217;s and Mars&#8217; radial distances, which can be used for analysing real CME events.

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MHD effects of the solar wind flow around planets

Nonlinear Processes in Geophysics ◽

10.5194/npg-7-201-2000 ◽

2000 ◽

Vol 7 (3/4) ◽

pp. 201-210 ◽

Cited By ~ 2

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.

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Compressive fluctuations in the solar wind and their polytropic index

Annales Geophysicae ◽

10.1007/s00585-996-0510-z ◽

1996 ◽

Vol 14 (5) ◽

pp. 510-517 ◽

Cited By ~ 6

Author(s):

B. Bavassano ◽

R. Bruno ◽

H. Rosenbauer

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Solar Rotation ◽

Polytropic Index ◽

Constant Density ◽

The Sun ◽

Thermal Pressure ◽

Fast Wind ◽

Pressure Equilibrium ◽

Interplanetary Plasma

Abstract. Magnetohydrodynamic compressive fluctuations of the interplanetary plasma in the region from 0.3 to 1 AU have been characterized in terms of their polytropic index. Following Chandrasekhar's approach to polytropic fluids, this index has been determined through a fit of the observed variations of density and temperature. At least three different classes of fluctuations have been identified: (1) variations at constant thermal pressure, in low-speed solar wind and without a significant dependence on distance, (2) adiabatic variations, mainly close to 1 AU and without a relevant dependence on wind speed, and (3) variations at nearly constant density, in fast wind close to 0.3 AU. Variations at constant thermal pressure are probably a subset of the ensemble of total-pressure balanced structures, corresponding to cases in which the magnetic field magnitude does not vary appreciably throughout the structure. In this case the pressure equilibrium has to be assured by its thermal component only. The variations may be related to small flow-tubes with approximately the same magnetic-field intensity, convected by the wind in conditions of pressure equilibrium. This feature is mainly observed in low-velocity solar wind, in agreement with the magnetic topology (small open flow-tubes emerging through an ensemble of closed structures) expected for the source region of slow wind. Variations of adiabatic type may be related to magnetosonic waves excited by pressure imbalances between contiguous flow-tubes. Such imbalances are probably built up by interactions between wind flows with different speeds in the spiral geometry induced by the solar rotation. This may account for the fact that they are mainly found at a large distance from the sun. Temperature variations at almost constant density are mostly found in fast flows close to the sun. These are the solar wind regions with the best examples of incompressible behaviour. They are characterized by very stable values for particle density and magnetic intensity, and by fluctuations of Alfvénic type. It is likely that temperature fluctuations in these regions are a remnant of thermal features in the low solar atmosphere. In conclusion, the polytropic index appears to be a useful tool to understand the nature of the compressive turbulence in the interplanetary plasma, as far as the frozen-in magnetic field does not play a crucial role.

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

Advances in Space Research ◽

10.1016/0273-1177(81)90092-2 ◽

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

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Solar-Wind Structure

Oxford Research Encyclopedia of Physics ◽

10.1093/acrefore/9780190871994.013.19 ◽

2020 ◽

Author(s):

Mathew J. Owens

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interstellar Medium ◽

Solar Atmosphere ◽

Solar Surface ◽

Spatial Scales ◽

The Sun ◽

Archimedean Spiral ◽

Fast Wind ◽

Slow Wind

The hot solar atmosphere continually expands out into space to form the solar wind, which drags with it the Sun’s magnetic field. This creates a cavity in the interstellar medium, extending far past the outer planets, within which the solar magnetic-field dominates. While the physical mechanisms by which the solar atmosphere is heated are still debated, the resulting solar wind can be readily understood in terms of the pressure difference between the hot, dense solar atmosphere and the cold, tenuous interstellar medium. This results in an accelerating solar-wind profile which becomes supersonic long before it reaches Earth orbit. The large-scale structure of the magnetic field carried by the solar wind is that of an Archimedean spiral, owing to the radial solar-wind flow away from the Sun and the rotation of the magnetic footpoints with the solar surface. Within this relatively simple picture, however, is a range of substructure, on all observable time and spatial scales. Solar-wind flows are largely bimodal in character. “Fast” wind comes from open magnetic-field regions, which have a single connection to the solar surface. “Slow” wind, on the other hand, appears to come from the vicinity of closed magnetic field regions, which have both ends connected to the Sun. Interaction of fast and slow wind leads to patterns of solar-wind compression and expansion which sweep past Earth. Within this relatively stable structure of flows, huge episodic eruptions of solar material further perturb conditions. At the smaller scales, turbulent eddies create unpredictable variations in solar-wind conditions. These solar-wind structures are of great interest as they give rise to space weather that can adversely affect space- and ground-based technologies, as well as pose a threat to humans in space.

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(Non)-radial propagation of the solar wind flow

10.5194/egusphere-egu2020-2736 ◽

2020 ◽

Author(s):

Zdeněk Němeček ◽

Tereza Ďurovcová ◽

Jana Šafránková ◽

Jiří Šimůnek ◽

John D. Richardson ◽

...

Keyword(s):

Solar Wind ◽

Radial Velocity ◽

Orbital Motion ◽

Wind Flow ◽

The Sun ◽

Mars Express ◽

The Earth ◽

Solar Wind Flow ◽

Magnetospheric Tail ◽

Radial Propagation

The solar wind aberration due to non-radial velocity components and the Earth orbital motion is important for the overall magnetosphere geometry because the magnetospheric tail is aligned with the solar wind flow. This paper investigates an evolution of non-radial components of the solar wind flow along the path from the Sun to 6 AU. A comparison of observations at 1 AU and closer to or further from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Wind, ACE, Spektr-R, THEMIS B and C, Helios 1 and 2, Mars-Express, Voyager 1 and 2) shows that (i) the average values of non-radial components vary with the distance from the Sun and (ii) they differ according to solar wind streams.

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Influence of the Interplanetary Magnetic Field on the Solar Wind Flow about Planetary Obstacles

Space Science Reviews ◽

10.1007/s11214-006-6059-z ◽

2006 ◽

Vol 122 (1-4) ◽

pp. 209-219 ◽

Cited By ~ 5

Author(s):

Nikolai Erkaev ◽

Alexander Mezentsev ◽

Helfried Biernat

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interplanetary Magnetic Field ◽

Wind Flow ◽

Solar Wind Flow

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INFLUENCE OF THE AMBIENT SOLAR WIND FLOW ON THE PROPAGATION BEHAVIOR OF INTERPLANETARY CORONAL MASS EJECTIONS

The Astrophysical Journal ◽

10.1088/0004-637x/743/2/101 ◽

2011 ◽

Vol 743 (2) ◽

pp. 101 ◽

Cited By ~ 69

Author(s):

Manuela Temmer ◽

Tanja Rollett ◽

Christian Möstl ◽

Astrid M. Veronig ◽

Bojan Vršnak ◽

...

Keyword(s):

Solar Wind ◽

Coronal Mass Ejections ◽

Wind Flow ◽

Interplanetary Coronal Mass Ejections ◽

Propagation Behavior ◽

Solar Wind Flow ◽

Ambient Solar Wind

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

10.5194/egusphere-egu2020-3029 ◽

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

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

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Plasma processes at comet Churyumov–Gerasimenko: Expectations for Rosetta

Journal of Plasma Physics ◽

10.1017/s0022377813001116 ◽

2013 ◽

Vol 79 (6) ◽

pp. 1067-1070 ◽

Cited By ~ 1

Author(s):

D. A. MENDIS ◽

M. HORÁNYI

Keyword(s):

Solar Wind ◽

Solar Radiation ◽

Bow Shock ◽

Short Paper ◽

Wind Flow ◽

The Sun ◽

Cometary Plasma ◽

Variable Nature ◽

Solar Wind Flow ◽

Comet 67P

AbstractThe Rosetta–Philae mission to comet 67P/Churyumov–Gerasimenko in 2014 will provide a unique opportunity to observe the variable nature of the interaction of a comet with the solar radiation and the solar wind, as the comet approaches the Sun. In this short paper we will focus on the varying global structure of the cometary plasma environment. Specifically we make predictions on the varying locations of the two basic transitions in the global, contaminated solar wind flow toward the comet: the outer bow shock and the ionopause.

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