scholarly journals Variations and Effects of the Venusian Bow Shock from VEX Mission

2012 ◽  
Vol 8 (S293) ◽  
pp. 329-332
Author(s):  
Yansong Xue ◽  
Shuanggen Jin
Keyword(s):  
Solar Wind ◽  
Solar Maximum ◽  
Direct Interaction ◽  
Magnetic Pressure ◽  
Bow Shock ◽  
Bow Shocks ◽  
Venus Express ◽  
Inner Region ◽  
Planetary Magnetic Field ◽  
Atmosphere Of Venus

AbstractThe upper atmosphere of Venus is not shielded by planetary magnetic field from direct interaction with the solar wind. The interaction of shocked solar wind and the ionosphere results in ionopause. Magnetic barrier, the inner region of dayside magnetosheath with the dominated magnetic pressure deflects the solar wind instead of the ionopause at solar maximum. Therefore, the structure and interaction of venusian ionosphere is very complex. Although the Venus Express (VEX) arrived at Venus in April 2006 provides more knowledge on the Venusian ionosphere and plasma environment, compared to Pioneer Venus Orbiter (PVO) with about 14 years of observations, some important details are still unknown (e.g., long Venusian bow shock variations and effects). In this paper, the bow shock positions of Venus are determined and analyzed from magnetometer (MAG) and ASPERA-4 of the Venus Express mission from May 28, 2006 to August 17, 2010. Results show that the altitude of BS was mainly affected by SZA (solar zenith angle) and Venus bow shocks inbound and outbound are asymmetry.

scholarly journals The spectral scalings of magnetic fluctuations upstream and downstream of the Venusian bow shock

2020 ◽  
Author(s):  
S. D. XIAO ◽  
M. Y. Wu ◽  
G. Q. Wang ◽  
Y. Q. Chen ◽  
T. L. Zhang
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Energy Cascade ◽  
Kinetic Regime ◽  
Magnetic Fluctuations ◽  
Solar Wind Interaction ◽  
Bow Shocks ◽  
Venus Express ◽  
Statistical Results

Abstract We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel ( {Q}_{\parallel } ) bow shock crossings and 303 quasi-perpendicular ( {Q}_{\perp } ) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the {Q}_{\parallel } and {Q}_{\perp } bow shock is basically consistent. While the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the {Q}_{\parallel } bow shocks are not as significant as near the {Q}_{\perp } bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the {Q}_{\parallel } bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the {Q}_{\parallel } bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus.

scholarly journals Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars

2011 ◽  
Vol 29 (3) ◽  
pp. 511-528 ◽  
Author(s):  
M. Yamauchi ◽  
Y. Futaana ◽  
A. Fedorov ◽  
R. A. Frahm ◽  
J. D. Winningham ◽  
...  
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Bow Shock ◽  
Large Field ◽  
Upstream Region ◽  
Magnetic Field Direction ◽  
Mars Express ◽  
Energy Domain ◽  
Bow Shocks ◽  
Venus Express

Abstract. Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy) that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a field-aligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward interplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and effects of cold ion abundance in the bow shock are discussed.

scholarly journals Radial dependence of foreshock cavities: a case study

2004 ◽  
Vol 22 (12) ◽  
pp. 4143-4151 ◽  
Author(s):  
D. G. Sibeck ◽  
K. Kudela ◽  
T. Mukai ◽  
Z. Nemecek ◽  
J. Safrankova
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Bow Shock ◽  
Radial Dependence ◽  
Energetic Ions ◽  
Interplanetary Physics ◽  
Bow Shocks

Abstract. We present a case study of Geotail, Interball-1, IMP-8, and Wind observations of density and magnetic field strength cavities excavated by the enhanced pressures associated with bursts of energetic ions in the foreshock. Consistent with theoretical predictions, the pressure of the energetic ions diminishes rapidly with upstream distance due to a decrease in the flux of energetic ions and a transition from near-isotropic to streaming pitch angle distributions. Consequently, the cavities can only be observed immediately upstream from the bow shock. A comparison of conditions upstream from the pre- and post-noon bow shock demonstrates that foreshock cavities introduce perturbations into the oncoming solar wind flow with dimensions smaller than those of the magnetosphere. Dayside geosynchronous magnetic field strength variations observed by GOES-8 do not track the density variations seen by any of the spacecraft upstream from the bow shock in a one-to-one manner, indicating that none of these spacecraft observed the precise sequence of density variations that actually struck the subsolar magnetopause. Key words. Interplanetary physics (energetic particles; planetary bow shocks) – Magnetospheric physics (solar wind-magnetosphere interactions)

scholarly journals The spectral scalings of magnetic fluctuations upstream and downstream of the Venusian bow shock

2020 ◽  
Author(s):  
S. D. XIAO ◽  
M. Y. Wu ◽  
G. Q. Wang ◽  
Y. Q. Chen ◽  
T. L. Zhang
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Energy Cascade ◽  
Kinetic Regime ◽  
Magnetic Fluctuations ◽  
Solar Wind Interaction ◽  
Large Dispersion ◽  
Key Factor ◽  
Bow Shocks ◽  
Statistical Results

Abstract We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel (Q ∥ ) bow shock crossings and 303 quasi-perpendicular (Q ⊥ ) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the Q ∥ and Q ⊥ bow shock is basically consistent. While the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the Q ∥ bow shocks are not as significant as near the Q ⊥ bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the Q ∥ bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the Q ∥ bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus. The large dispersion of spectral scalings indicates that this fluctuation environment is complicated, and the shock geometry is not the only key factor in the fluctuations across the Venusian bow shock. Other possible factors in the shock modification to the upstream fluctuations will be explored in future.

scholarly journals Magnetosheath plasma flow model around Mercury

2021 ◽  
Author(s):  
Daniel Schmid ◽  
Ferdinand Plaschke ◽  
Yasuhito Narita ◽  
Martin Volwerk ◽  
Rumi Nakamura ◽  
...  
Keyword(s):  
Solar Wind ◽  
Plasma Flow ◽  
Flow Model ◽  
Outer Boundary ◽  
Solar Wind Plasma ◽  
Bow Shock ◽  
Plasma Parameters ◽  
Upstream Solar Wind ◽  
Planetary Magnetic Field ◽  
Spacecraft Location

Abstract. The magnetosheath is defined as the plasma region between the bow shock, where the super-magnetosonic solar wind plasma is decelerated and heated, and the outer boundary of the intrinsic planetary magnetic field, the so called magnetopause. Based on the Soucek-Escoubet magnetosheath flow model at Earth, we present the first analytical magnetosheath plasma flow model for Mercury. It can be used to estimate the plasma flow magnitude and direction at any given point in the magnetosheath exclusively on the basis of the plasma parameters of the upstream solar wind. The aim of this paper is to provide a tool to back-trace the magnetosheath plasma flow between multiple observation points or from a given spacecraft location to the bow shock.

scholarly journals Injection and acceleration of H<sup>+</sup> and He<sup>2+</sup> at Earth's bow shock

1999 ◽  
Vol 17 (5) ◽  
pp. 583-594 ◽  
Author(s):  
M. Scholer ◽  
H. Kucharek ◽  
K.-H. Trattner
Keyword(s):  
Solar Wind ◽  
Ion Beam ◽  
Background Field ◽  
Bow Shock ◽  
Acceleration Process ◽  
Magnetic Fluctuations ◽  
Folding Energy ◽  
Interplanetary Physics ◽  
Earth’S Bow Shock ◽  
Bow Shocks

Abstract. We have performed a number of one-dimensional hybrid simulations (particle ions, massless electron fluid) of quasi-parallel collisionless shocks in order to investigate the injection and subsequent acceleration of part of the solar wind ions at the Earth's bow shock. The shocks propagate into a medium containing magnetic fluctuations, which are initially superimposed on the background field, as well as generated or enhanced by the electromagnetic ion/ion beam instability between the solar wind and backstreaming ions. In order to study the mass (M) and charge (Q) dependence of the acceleration process He2+ is included self-consistently. The upstream differential intensity spectra of H+ and He2+ can be well represented by exponentials in energy. The e-folding energy Ec is a function of time: Ec increases with time. Furthermore the e-folding energy (normalized to the shock ramming energy Ep) increases with increasing Alfvén Mach number of the shock and with increasing fluctuation level of the initially superimposed turbulence. When backstreaming ions leave the shock after their first encounter they exhibit already a spectrum which extends to more than ten times the shock ramming energy and which is ordered in energy per charge. From the injection spectrum it is concluded that leakage of heated downstream particles does not contribute to ion injection. Acceleration models that permit thermal particles to scatter like the non-thermal population do not describe the correct physics.Key words. Interplanetary physics (planetary bow shocks) · Space plasma physics (charged particle motion and acceleration; numerical simulation studies)

scholarly journals Spatial distribution of upstream magnetospheric ≥50 keV ions

2000 ◽  
Vol 18 (1) ◽  
pp. 42-46 ◽  
Author(s):  
G. C. Anagnostopoulos ◽  
G. Argyropoulos ◽  
G. Kaliabetsos
Keyword(s):  
Solar Wind ◽  
Statistical Analysis ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Bow Shock ◽  
Occurrence Frequency ◽  
Ion Distributions ◽  
Interplanetary Physics ◽  
Earth’S Bow Shock ◽  
Bow Shocks

Abstract. We present for the first time a statistical study of \\geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1) a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT) of the bow shock, (2) highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF) configuration, and (3) a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1) preferential leakage of ~50 keV magnetospheric ions from the dusk magnetopause, (2) nearly scatter free motion of ~50 keV ions within the magnetosheath, and (3) final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV) upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between ~16%-~34% in the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks)

scholarly journals The spectral scalings of magnetic fluctuations upstream and downstream of the Venusian bow shock

2020 ◽  
Author(s):  
S. D. XIAO ◽  
M. Y. Wu ◽  
G. Q. Wang ◽  
Y. Q. Chen ◽  
T. L. Zhang
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Energy Cascade ◽  
Kinetic Regime ◽  
Magnetic Fluctuations ◽  
Solar Wind Interaction ◽  
Large Dispersion ◽  
Key Factor ◽  
Bow Shocks ◽  
Statistical Results

Abstract We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel (Q∥) bow shock crossings and 303 quasi-perpendicular (Q⊥) bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/f noise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for the Q∥ and Q⊥ bow shock is basically consistent. While the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the Q∥ bow shocks are not as significant as near the Q⊥ bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the Q∥ bow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and the Q∥ bow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus. The large dispersion of spectral scalings indicates that this fluctuation environment is complicated, and the shock geometry is not the only key factor in the fluctuations across the Venusian bow shock. Other possible factors in the shock modification to the upstream fluctuations will be explored in future.

Energy conversion at the terrestrial bow shock

2020 ◽  
Author(s):  
Maria Hamrin ◽  
Ramon Lopez ◽  
Pauline Dredger ◽  
Herbert Gunell ◽  
Oleksandr Goncharov ◽  
...  
Keyword(s):  
Solar Wind ◽  
Particle Acceleration ◽  
Energy Conversion ◽  
Mechanical Energy ◽  
Bow Shock ◽  
Passive Element ◽  
Magnetospheric Multiscale ◽  
Bow Shocks ◽  
Current Systems ◽  
The Magnetic Field

&lt;p&gt;At Earth&amp;#8217;s bow shock, the supersonic solar wind is slowed down and deflected around the magnetosphere. To many this is &quot;just a bow shock&quot;, a simple and quite passive element of solar-terrestrial physics. However, it has recently been realized that the bow shock plays a significantly more important role with currents on the bow shock connecting through the magnetosheath to the magnetospheric current systems. The bow shock current cannot close locally, since the magnetic field compression in the magnetosheath cannot be maintained globally. The bow shock current is inevitably a generator current extracting mechanical energy from the supersonic solar wind, and feeding it to other processes such as acceleration of the magnetosheath flow, local particle acceleration at the bow shock and dissipation in the distant ionosphere. Here we use data from the first dayside season of the Magnetospheric Multiscale (MMS) mission to investigate the generator properties of the terrestrial bow shock. Typically, the main shock ramp shows clear generator properties, but for some of the more turbulent bow shocks, generator properties may also be observed slightly downstream the ramp. This may be due to effects from shock motions and shock nonstationaity and reformation. Moreover, sometimes a weaker load can be seen in the upstream foot region due to local particle acceleration. We also find that the generator capacity of the bow shock decreases with decreasing bow shock angle as well as with increasing upstream plasma beta and solar Mach number. A better understanding of the energy conversion properties of the terrestrial bow shock will be useful also for the understanding of other astrophysical shock currents. The currents must close somewhere and deposit energy somewhere.&lt;/p&gt;

scholarly journals Mirror mode waves in Venus's magnetosheath: solar minimum vs. solar maximum

2016 ◽  
Vol 34 (11) ◽  
pp. 1099-1108 ◽  
Author(s):  
Martin Volwerk ◽  
Daniel Schmid ◽  
Bruce T. Tsurutani ◽  
Magda Delva ◽  
Ferdinand Plaschke ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Solar Wind Velocity ◽  
Solar Maximum ◽  
Flow Line ◽  
Bow Shock ◽  
Solar Wind Density ◽  
Solar Uv ◽  
Mirror Mode ◽  
Possible Cause

Abstract. The observational rate of mirror mode waves in Venus's magnetosheath for solar maximum conditions is studied and compared with previous results for solar minimum conditions. It is found that the number of mirror mode events is approximately 14 % higher for solar maximum than for solar minimum. A possible cause is the increase in solar UV radiation, ionizing more neutrals from Venus's exosphere and the outward displacement of the bow shock during solar maximum. Also, the solar wind properties (speed, density) differ for solar minimum and maximum. The maximum observational rate, however, over Venus's magnetosheath remains almost the same, with only differences in the distribution along the flow line. This may be caused by the interplay of a decreasing solar wind density and a slightly higher solar wind velocity for this solar maximum. The distribution of strengths of the mirror mode waves is shown to be exponentially falling off, with (almost) the same coefficient for solar maximum and minimum. The plasma conditions in Venus's magnetosheath are different for solar minimum as compared to solar maximum. For solar minimum, mirror mode waves are created directly behind where the bow shock will decay, whereas for solar maximum all created mirror modes can grow.

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