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 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 Low-frequency magnetic variations at the high-<i>β</i> Earth bow shock

2019 ◽  
Vol 37 (5) ◽  
pp. 877-889
Author(s):  
Anatoli A. Petrukovich ◽  
Olga M. Chugunova ◽  
Pavel I. Shustov
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Spatial Scales ◽  
Low Frequency ◽  
Background Field ◽  
Bow Shock ◽  
Stable Phase ◽  
Main Magnetic Field ◽  
Astrophysical Plasmas ◽  
Earth’S Bow Shock

Abstract. Observations of Earth's bow shock during high-β (ratio of thermal to magnetic pressure) solar wind streams are rare. However, such shocks are ubiquitous in astrophysical plasmas. Typical solar wind parameters related to high β (here β>10) are as follows: low speed, high density, and a very low interplanetary magnetic field of 1–2 nT. These conditions are usually quite transient and need to be verified immediately upstream of the observed shock crossings. In this report, three characteristic crossings by the Cluster project (from the 22 found) are studied using multipoint analysis, allowing us to determine spatial scales. The main magnetic field and density spatial scale of about a couple of hundred of kilometers generally corresponds to the increased proton convective gyroradius. Observed magnetic variations are different from those for supercritical shocks, with β∼1. Dominant magnetic variations in the shock transition have amplitudes much larger than the background field and have a frequency of ∼ 0.3–0.5 Hz (in some events – 1–2 Hz). The wave polarization has no stable phase and is closer to linear, which complicates the determination of the wave propagation direction. Spatial scales (wavelengths) of variations are within several tens to a couple of hundred of kilometers.

scholarly journals Energy time dispersion of a new class of magnetospheric ion events observed near the Earth's bow shock

2000 ◽  
Vol 18 (1) ◽  
pp. 28-41 ◽  
Author(s):  
G. C. Anagnostopoulos ◽  
N. Paschalidis ◽  
A. N. Littas
Keyword(s):  
Time Resolution ◽  
Bow Shock ◽  
High Time ◽  
High Time Resolution ◽  
Energy Dispersion ◽  
New Class ◽  
Interplanetary Physics ◽  
Earth’S Bow Shock ◽  
Bow Shocks ◽  
Dependent Transport

Abstract. We have analyzed high time resolution (\\geq6 s) data during the onset and the decay phase of several energetic (\\geq35 keV) ion events observed near the Earth's bow shock by the CCE/AMPTE and IMP-7/8 spacecraft, during times of intense substorm/geomagnetic activity. We found that forward energy dispersion at the onset of events (earlier increase of middle energy ions) and/or a delayed fall of the middle energy ion fluxes at the end of events are often evident in high time resolution data. The energy spectra at the onset and the decay of this kind of events show a characteristic hump at middle (50-120 keV) energies and the angular distributions display either anisotropic or broad forms. The time scale of energy dispersion in the ion events examined was found to range from several seconds to \\sim1 h depending on the ion energies compared and on the rate of variation of the Interplanetary Magnetic Field (IMF) direction. Several canditate processes are discussed to explain the observations and it is suggested that a rigidity dependent transport process of magnetospheric particles within the magnetosheath is most probably responsible for the detection of this new type of near bow shock magnetospheric ion events. The new class of ion events was observed within both the magnetosheath and 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.

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 Observations of the spatial and temporal structure of field-aligned beam and gyrating ring distributions at the quasi-perpendicular bow shock with Cluster CIS

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1411-1420 ◽  
Author(s):  
E. Möbius ◽  
H. Kucharek ◽  
C. Mouikis ◽  
E. Georgescu ◽  
L. M. Kistler ◽  
...  
Keyword(s):  
Specular Reflection ◽  
Temporal Structure ◽  
Bow Shock ◽  
Ion Distribution ◽  
Angle Scattering ◽  
Major Species ◽  
Interplanetary Physics ◽  
Earth’S Bow Shock ◽  
Bow Shocks ◽  
Cluster Ion

Abstract. During the early orbit phase, the Cluster spacecraft have repeatedly crossed the perpendicular Earth’s bow shock and provided the first multi-spacecraft measurements. We have analyzed data from the Cluster Ion Spectrometry experiment (CIS), which observes the 3D-ion distribution function of the major species in the energy range of 5 eV to 40 keV with a 4 s resolution. Beams of reflected ions were observed simultaneously at all spacecraft locations and could be tracked from upstream to the shock itself. They were found to originate from the same distribution of ions that constitutes the reflected gyrating ions, which form a ring distribution in the velocity space immediately upstream and downstream of the shock. This observation suggests a common origin of ring and beam populations at quasi-perpendicular shocks in the form of specular reflection and immediate pitch angle scattering. Generally, the spatial evolution across the shock is very similar on all spacecraft, but phased in time according to their relative location. However, a distinct temporal structure of the ion fluxes in the field-aligned beam is observed that varies simultaneously on all spacecraft. This is likely to reflect the variations in the reflection and scattering efficiencies.Key words. Interplanetary physics (planetary bow shocks; energetic particles; instruments and techniques)

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

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 Global MHD Simulations of the Earth's Bow Shock Shape and Motion Under Variable Solar Wind Conditions

2018 ◽  
Vol 123 (1) ◽  
pp. 259-271 ◽  
Author(s):  
L. Mejnertsen ◽  
J. P. Eastwood ◽  
H. Hietala ◽  
S. J. Schwartz ◽  
J. P. Chittenden
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Mhd Simulations ◽  
Earth’S Bow Shock
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