On the role of the magnetic field in the solar wind interaction with venus: Expectations versus observations

Abstract. We present a statistical survey of large-amplitude, asymmetric plasma and magnetic field enhancements detected outside the diamagnetic cavity at comet 67P/Churyumov–Gerasimenko from December 2014 to June 2016. Based on the concurrent observations of plasma and magnetic field enhancements, we interpret them to be magnetosonic waves. The aim is to provide a general overview of these waves' properties over the mission duration. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of these waves and their characteristics. In total, we identified ∼ 70 000 steepened waves in the magnetic field data by means of machine learning. We observe that the occurrence of these steepened waves is linked to the activity of the comet, where steepened waves are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressional nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual steepened waves. With increasing mass loading, the average amplitude of the waves decreases, while the skewness increases. Using a modified 1D magnetohydrodynamic (MHD) model, we investigated if the waves can be described by the combination of nonlinear and dissipative effects. By combining the model with observations of amplitude, width and skewness, we obtain an estimate of the effective plasma diffusivity in the comet–solar wind interaction region and compare it with suitable reference values as a consistency check. At 67P/Churyumov–Gerasimenko, these steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

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Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov-Gerasimenko

10.5194/angeo-2020-84 ◽

2020 ◽

Author(s):

Katharina Ostaszewski ◽

Karl-Heinz Glassmeier ◽

Charlotte Goetz ◽

Philip Heinisch ◽

Pierre Henri ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interaction Region ◽

Occurrence Rate ◽

Solar Wind Interaction ◽

Plasma Properties ◽

Background Magnetic Field ◽

The Waves ◽

Comet 67P ◽

The Magnetic Field

Abstract. We present a statistical survey of large amplitude, asymmetric plasma, and magnetic field enhancements at comet 67P/Churyumov-Gerasimenko from December 2014 to June 2016. The aim is to provide a general overview of these structures' properties over the mission duration. At comets, nonlinear wave evolution plays an integral part in the development of turbulence and in particular facilitates the transfer of energy and momentum. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of steepened waves and their characteristics. In total, we identified ~70000 events in the magnetic field data by means of machine learning. We observe that the occurrence of wave events is linked to the activity of the comet, where events are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressive nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual events. With increasing massloading the average amplitude of steepened waves decreases while the skewness increases. Using a modified 1D MHD model it was possible to show that such solitary structures can be described by the combination of nonlinear, dispersive, and dissipative effects. By combining the model with observations of amplitude, width, and skewness we obtain an estimate of the effective plasma viscosity in the comet-solar wind interaction region. At 67P/Churyumov-Gerasimenko steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

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Oxygen ion escape from Venus in a global hybrid simulation: role of the ionospheric O<sup>+</sup> ions

Annales Geophysicae ◽

10.5194/angeo-27-4333-2009 ◽

2009 ◽

Vol 27 (11) ◽

pp. 4333-4348 ◽

Cited By ~ 26

Author(s):

R. Jarvinen ◽

E. Kallio ◽

P. Janhunen ◽

S. Barabash ◽

T. L. Zhang ◽

...

Keyword(s):

Solar Wind ◽

Hybrid Simulation ◽

Solar Wind Interaction ◽

Simulation Code ◽

Oxygen Ion ◽

Ion Escape ◽

Global Configuration ◽

Best Fit ◽

The Magnetic Field

Abstract. We study the solar wind induced oxygen ion escape from Venus' upper atmosphere and the Venus Express observations of the Venus-solar wind interaction by the HYB-Venus hybrid simulation code. We compare the simulation to the magnetic field and ion observations during an orbit of nominal upstream conditions. Further, we study the response of the induced magnetosphere to the emission of planetary ions. The hybrid simulation is found to be able to reproduce the main observed regions of the Venusian plasma environment: the bow shock (both perpendicular and parallel regions), the magnetic barrier, the central tail current sheet, the magnetic tail lobes, the magnetosheath and the planetary wake. The simulation is found to best fit the observations when the planetary \\oxy~escape rate is in the range from 3×1024 s−1 to 1.5×1025 s−1. This range was also found to be a limit for a test particle-like behaviour of the planetary ions: the higher escape rates manifest themselves in a different global configuration of the Venusian induced magnetosphere.

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Aspects of solar wind interaction with Mars: comparison of fluid and hybrid simulations

Annales Geophysicae ◽

10.5194/angeo-25-145-2007 ◽

2007 ◽

Vol 25 (1) ◽

pp. 145-159

Author(s):

N. V. Erkaev ◽

A. Bößwetter ◽

U. Motschmann ◽

H. K. Biernat

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Hybrid Model ◽

Field Enhancement ◽

Bow Shock ◽

Solar Wind Interaction ◽

Plasma Parameters ◽

Physical Reason ◽

The Magnetic Field ◽

Hybrid Simulations

Abstract. Mars has no global intrinsic magnetic field, and consequently the solar wind plasma interacts directly with the planetary ionosphere. The main factors of this interaction are: thermalization of plasma after the bow shock, ion pick-up process, and the magnetic barrier effect, which results in the magnetic field enhancement in the vicinity of the obstacle. Results of ideal magnetohydrodynamic and hybrid simulations are compared in the subsolar magnetosheath region. Good agreement between the models is obtained for the magnetic field and plasma parameters just after the shock front, and also for the magnetic field profiles in the magnetosheath. Both models predict similar positions of the proton stoppage boundary, which is known as the ion composition boundary. This comparison allows one to estimate applicability of magnetohydrodynamics for Mars, and also to check the consistency of the hybrid model with Rankine-Hugoniot conditions at the bow shock. An additional effect existing only in the hybrid model is a diffusive penetration of the magnetic field inside the ionosphere. Collisions between ions and neutrals are analyzed as a possible physical reason for the magnetic diffusion seen in the hybrid simulations.

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What Density of Magnetosheath Sodium Ions Can Provide the Observed Decrease in the Magnetic Field of the “Double Magnetopause” during the First MESSENGER Flyby?

Symmetry ◽

10.3390/sym13071168 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1168

Author(s):

Elena Belenkaya ◽

Ivan Pensionerov

Keyword(s):

Magnetic Field ◽

Analytical Approach ◽

Field Structure ◽

Sodium Ions ◽

Plasma Parameters ◽

Calculation Results ◽

Magnetizing Current ◽

The Magnetic Field ◽

Density Excess

On 14 January 2008, the MESSENGER spacecraft, during its first flyby around Mercury, recorded the magnetic field structure, which was later called the “double magnetopause”. The role of sodium ions penetrating into the Hermean magnetosphere from the magnetosheath in generation of this structure has been discussed since then. The violation of the symmetry of the plasma parameters at the magnetopause is the cause of the magnetizing current generation. Here, we consider whether the change in the density of sodium ions on both sides of the Hermean magnetopause could be the cause of a wide diamagnetic current in the magnetosphere at its dawn-side boundary observed during the first MESSENGER flyby. In the present paper, we propose an analytical approach that made it possible to determine the magnetosheath Na+ density excess providing the best agreement between the calculation results and the observed magnetic field in the double magnetopause.

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Cluster observations of sudden impulses in the magnetotail caused by interplanetary shocks and pressure increases

Annales Geophysicae ◽

10.5194/angeo-23-609-2005 ◽

2005 ◽

Vol 23 (2) ◽

pp. 609-624 ◽

Cited By ~ 26

Author(s):

K. E. J. Huttunen ◽

J. Slavin ◽

M. Collier ◽

H. E. J. Koskinen ◽

A. Szabo ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Dynamic Pressure ◽

Solar Wind Speed ◽

Interplanetary Shock ◽

Wind Pressure ◽

Shock Propagation ◽

Interplanetary Shocks ◽

Maximum Variance ◽

The Magnetic Field

Abstract. Sudden impulses (SI) in the tail lobe magnetic field associated with solar wind pressure enhancements are investigated using measurements from Cluster. The magnetic field components during the SIs change in a manner consistent with the assumption that an antisunward moving lateral pressure enhancement compresses the magnetotail axisymmetrically. We found that the maximum variance SI unit vectors were nearly aligned with the associated interplanetary shock normals. For two of the tail lobe SI events during which Cluster was located close to the tail boundary, Cluster observed the inward moving magnetopause. During both events, the spacecraft location changed from the lobe to the magnetospheric boundary layer. During the event on 6 November 2001 the magnetopause was compressed past Cluster. We applied the 2-D Cartesian model developed by collier98 in which a vacuum uniform tail lobe magnetic field is compressed by a step-like pressure increase. The model underestimates the compression of the magnetic field, but it fits the magnetic field maximum variance component well. For events for which we could determine the shock normal orientation, the differences between the observed and calculated shock propagation times from the location of WIND/Geotail to the location of Cluster were small. The propagation speeds of the SIs between the Cluster spacecraft were comparable to the solar wind speed. Our results suggest that the observed tail lobe SIs are due to lateral increases in solar wind dynamic pressure outside the magnetotail boundary.

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Solar wind and substorm excitation of the wavy current sheet

Annales Geophysicae ◽

10.5194/angeo-27-2457-2009 ◽

2009 ◽

Vol 27 (6) ◽

pp. 2457-2474 ◽

Cited By ~ 25

Author(s):

C. Forsyth ◽

M. Lester ◽

R. C. Fear ◽

E. Lucek ◽

I. Dandouras ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Current Sheet ◽

Pressure Pulse ◽

Wind Pressure ◽

Expansion Velocity ◽

Solar Wind Pressure ◽

Wave Models ◽

Best Fit ◽

The Magnetic Field

Abstract. Following a solar wind pressure pulse on 3 August 2001, GOES 8, GOES 10, Cluster and Polar observed dipolarizations of the magnetic field, accompanied by an eastward expansion of the aurora observed by IMAGE, indicating the occurrence of two substorms. Prior to the first substorm, the motion of the plasma sheet with respect to Cluster was in the ZGSM direction. Observations following the substorms show the occurrence of current sheet waves moving predominantly in the −YGSM direction. Following the second substorm, the current sheet waves caused multiple current sheet crossings of the Cluster spacecraft, previously studied by Zhang et al. (2002). We further this study to show that the velocity of the current sheet waves was similar to the expansion velocity of the substorm aurora and the expansion of the dipolarization regions in the magnetotail. Furthermore, we compare these results with the current sheet wave models of Golovchanskaya and Maltsev (2005) and Erkaev et al. (2008). We find that the Erkaev et al. (2008) model gives the best fit to the observations.

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Connecting a Star’s Convection Zone with its Corona

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000020245 ◽

1995 ◽

Vol 12 (2) ◽

pp. 180-185 ◽

Cited By ~ 2

Author(s):

D. J. Galloway ◽

C. A. Jones

Keyword(s):

Magnetic Field ◽

Convection Zone ◽

Flux Rope ◽

Field System ◽

Stellar Convection ◽

Coronal Activity ◽

Flux Concentration ◽

Global Understanding ◽

The Magnetic Field

AbstractThis paper discusses problems which have as their uniting theme the need to understand the coupling between a stellar convection zone and a magnetically dominated corona above it. Interest is concentrated on how the convection drives the atmosphere above, loading it with the currents that give rise to flares and other forms of coronal activity. The role of boundary conditions appears to be crucial, suggesting that a global understanding of the magnetic field system is necessary to explain what is observed in the corona. Calculations are presented which suggest that currents flowing up a flux rope return not in the immediate vicinity of the rope but rather in an alternative flux concentration located some distance away.

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