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

2021 ◽  
Vol 73 (1) ◽  
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

AbstractWe 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 ($$Q_{\parallel }$$ Q ‖ ) bow shock crossings and 303 quasi-perpendicular ($$Q_{ \bot }$$ 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 $$Q_{\parallel }$$ Q ‖ and $$Q_{ \bot }$$ Q ⊥ bow shocks is basically consistent. However, the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near the $$Q_{\parallel }$$ Q ‖ bow shocks are not as significant as near the $$Q_{ \bot }$$ Q ⊥ bow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across the $$Q_{\parallel }$$ 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 $$Q_{\parallel }$$ 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 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 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 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 MESSENGER and Venus Express observations of the solar wind interaction with Venus

2009 ◽  
Vol 36 (9) ◽  
Author(s):  
James A. Slavin ◽  
Mario H. Acuña ◽  
Brian J. Anderson ◽  
Stas Barabash ◽  
Mehdi Benna ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Interaction ◽  
Venus Express

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)

Modulation of the solar wind driven ion escape from unmagnetized planets by ultra-low-frequency foreshock waves in a global hybrid simulation

2020 ◽  
Author(s):  
Riku Jarvinen ◽  
Esa Kallio ◽  
Tuija Pulkkinen
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Low Frequency ◽  
Hybrid Simulation ◽  
Bow Shock ◽  
Upstream Region ◽  
Ulf Waves ◽  
Solar Wind Interaction ◽  
Ion Escape ◽  
A Charge

&lt;p&gt;We study the solar wind interaction with Venus in a 3-dimensional global hybrid model where ions are treated as particles and electrons are a charge-neutralizing fluid. We concentrate on large-scale ultra-low frequency (ULF) waves in the ion foreshock and how they affect the energization and escape of planetary ions. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is smaller than about 45 degrees. The magnetic connection with the bow shock allows backstreaming of the solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter the bow shock and transmit in the downstream region. We analyze the coupling of the ULF waves with the planetary ion acceleration and compare Venus and Mars in a global hybrid simulation.&lt;/p&gt;

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