A 3D Parametric Martian Bow Shock Model with the Effects of Mach Number, Dynamic Pressure, and the Interplanetary Magnetic Field

Abstract. It has recently been proposed that ripples inherent to the bow shock during radial interplanetary magnetic field (IMF) may produce local high speed flows in the magnetosheath. These jets can have a dynamic pressure much larger than the dynamic pressure of the solar wind. On 17 March 2007, several jets of this type were observed by the Cluster spacecraft. We study in detail these jets and their effects on the magnetopause, the magnetosphere, and the ionospheric convection. We find that (1) the jets could have a scale size of up to a few RE but less than ~6 RE transverse to the XGSE axis; (2) the jets caused significant local magnetopause perturbations due to their high dynamic pressure; (3) during the period when the jets were observed, irregular pulsations at the geostationary orbit and localised flow enhancements in the ionosphere were detected. We suggest that these inner magnetospheric phenomena were caused by the magnetosheath jets.

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Generation of dynamic pressure pulses downstream of the bow shock by variations in the interplanetary magnetic field orientation

Journal of Geophysical Research Atmospheres ◽

10.1029/95ja02985 ◽

1996 ◽

Vol 101 (A1) ◽

pp. 479-493 ◽

Cited By ~ 56

Author(s):

Y. Lin ◽

L. C. Lee ◽

M. Yan

Keyword(s):

Magnetic Field ◽

Interplanetary Magnetic Field ◽

Dynamic Pressure ◽

Bow Shock ◽

Field Orientation ◽

Magnetic Field Orientation ◽

Pressure Pulses

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Simulations of observed auroral brightening caused by solar wind dynamic pressure enhancements under different interplanetary magnetic field conditions

Journal of Geophysical Research Atmospheres ◽

10.1029/2010ja016318 ◽

2011 ◽

Vol 116 (A6) ◽

pp. n/a-n/a ◽

Cited By ~ 13

Author(s):

Z. Peng ◽

C. Wang ◽

Y. Q. Hu ◽

J. R. Kan ◽

Y. F. Yang

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interplanetary Magnetic Field ◽

Dynamic Pressure ◽

Field Conditions ◽

Solar Wind Dynamic Pressure

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Effect of geomagnetic activity, solar wind and parameters of interplanetary magnetic field on regularities in intermittency of Pi2 geomagnetic pulsations

Solnechno-Zemnaya Fizika ◽

10.12737/11551 ◽

2015 ◽

Vol 1 (3) ◽

pp. 11-20 ◽

Cited By ~ 3

Author(s):

Надежда Куражковская ◽

Nadezhda Kurazhkovskaya ◽

Борис Клайн ◽

Boris Klain

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interplanetary Magnetic Field ◽

Geomagnetic Activity ◽

Dynamic Pressure ◽

Cumulative Distribution ◽

Qualitative Assessment ◽

Geomagnetic Pulsations ◽

Magnetospheric Substorms ◽

Pi2 Pulsations

We present the results of investigation of the influence of geomagnetic activity, solar wind and parameters of the interplanetary magnetic field (IMF) on properties of the intermittency of midlatitude burst series of Pi2 geomagnetic pulsations observed during magnetospheric substorms on the nightside (substorm Pi2) and in the absence of these phenomena (nonsub-storm Pi2). We considered the index α as a main characteristic of intermittency of substorm and nonsubstorm Pi2 pulsations. The index α characterizes the slope of the cumulative distribution function of Pi2 burst amplitudes. The study indicated that the value and dynamics of the index α varies depending on the planetary geomagnetic activity, auroral activity and the intensity of magnetospheric ring currents. In addition, the forms of dependences of the index α on the density n, velocity V, dynamic pressure Pd of the solar wind and IMF Bx-component are different. The behavior of the index α depending on the module of B, By- and Bz-components is similar. We found some critical values of V, Pd, B, By- and Bz-components, after reaching of which the turbulence of the magnetotail plasma during substorm development is decreased. The revealed patterns of the intermittency of Pi2 pulsations can be used for qualitative assessment of turbulence level in the magnetotail plasma depending on changing interplanetary conditions.

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Kinetic simulations of high Mach shocks: PIC simulations vs in-situ measurements

10.5194/egusphere-egu21-556 ◽

2021 ◽

Author(s):

Artem Bohdan ◽

Martin Pohl ◽

Jacek Niemiec ◽

Paul J. Morris ◽

Yosuke Matsumoto ◽

...

Keyword(s):

Magnetic Field ◽

Mach Number ◽

Supernova Remnants ◽

Large Scale ◽

Bow Shock ◽

Electron Heating ◽

Weibel Instability ◽

High Mach Number ◽

High Mach

<p>High-Mach-number collisionless shocks are found in planetary systems and supernova remnants (SNRs). Electrons are heated at these shocks to temperatures well above the Rankine&#8211;Hugoniot prediction. However, the processes responsible for causing the electron heating are still not well understood. We use a set of large-scale particle-in-cell simulations of nonrelativistic shocks in the high-Mach-number regime to clarify the electron heating processes. The physical behavior of these shocks is defined by ion reflection at the shock ramp. Further interactions between the reflected ions and the upstream plasma excites electrostatic Buneman and two-stream ion&#8211;ion Weibel instabilities. Electrons are heated via shock surfing acceleration, the shock potential, magnetic reconnection, stochastic Fermi scattering, and shock compression. The main contributor is the shock potential. The magnetic field lines become tangled due to the Weibel instability, which allows for parallel electron heating by the shock potential. The constrained model of electron heating predicts an ion-to-electron temperature ratio within observed values at SNR shocks and in Saturn&#8217;s bow shock. We also present evidence for field amplification by the Weibel instability. The normalized magnetic field strength strongly correlates with the Alfvenic Mach number, as is in-situ observed at Saturn's bow shock.</p>

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Statistical analysis of the dependence of large-scale Birkeland currents on solar wind parameters

Annales Geophysicae ◽

10.5194/angeo-28-515-2010 ◽

2010 ◽

Vol 28 (2) ◽

pp. 515-530 ◽

Cited By ~ 35

Author(s):

H. Korth ◽

B. J. Anderson ◽

C. L. Waters

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Mach Number ◽

Electric Field ◽

Large Scale ◽

Dynamic Pressure ◽

Dominant Factor ◽

Total Current ◽

Current Densities ◽

Birkeland Currents

Abstract. The spatial distributions of large-scale field-aligned Birkeland currents have been derived using magnetic field data obtained from the Iridium constellation of satellites from February 1999 to December 2007. From this database, we selected intervals that had at least 45% overlap in the large-scale currents between successive hours. The consistency in the current distributions is taken to indicate stability of the large-scale magnetosphere–ionosphere system to within the spatial and temporal resolution of the Iridium observations. The resulting data set of about 1500 two-hour intervals (4% of the data) was sorted first by the interplanetary magnetic field (IMF) GSM clock angle (arctan(By/Bz)) since this governs the spatial morphology of the currents. The Birkeland current densities were then corrected for variations in EUV-produced ionospheric conductance by normalizing the current densities to those occurring for 0° dipole tilt. To determine the dependence of the currents on other solar wind variables for a given IMF clock angle, the data were then sorted sequentially by the following parameters: the solar wind electric field in the plane normal to the Earth–Sun line, Eyz; the solar wind ram pressure; and the solar wind Alfvén Mach number. The solar wind electric field is the dominant factor determining the Birkeland current intensities. The currents shift toward noon and expand equatorward with increasing solar wind electric field. The total current increases by 0.8 MA per mV m−1 increase in Eyz for southward IMF, while for northward IMF it is nearly independent of the electric field, increasing by only 0.1 MA per mV m−1 increase in Eyz. The dependence on solar wind pressure is comparatively modest. After correcting for the solar dynamo dependencies in intensity and distribution, the total current intensity increases with solar wind dynamic pressure by 0.4 MA/nPa for southward IMF. Normalizing the Birkeland current densities to both the median solar wind electric field and dynamic pressure effects, we find no significant dependence of the Birkeland currents on solar wind Alfvén Mach number.

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A new formulation for the ionospheric cross polar cap potential including saturation effects

Annales Geophysicae ◽

10.5194/angeo-23-3533-2005 ◽

2005 ◽

Vol 23 (11) ◽

pp. 3533-3547 ◽

Cited By ~ 41

Author(s):

A. J. Ridley

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Mach Number ◽

Interplanetary Magnetic Field ◽

Polar Cap ◽

Pressure Balance ◽

Simple Modification ◽

Post Shock ◽

Cross Polar Cap Potential ◽

New Formulation

Abstract. It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) Bz becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12mV/m at some time. When these events are examined as typically done in previous studies, all of them show some signs of saturation (i.e., over-prediction of the CPCP based on a linear relationship between the IMF and the CPCP). We show that by taking into account the size of the magnetosphere and the fact that the post-shock magnetic field strength is strongly dependent upon the solar wind Mach number, we can better specify the ionospheric CPCP. The CPCP (Φ) can be expressed as Φ=(10-4v2+11.7B(1-e-Ma/3)sin3(θ/2)) {rms/9 (where v is the solar wind velocity, B is the combined Y and Z components of the interplanetary magnetic field, Ma is the solar wind Mach number, θ=acos(Bz/B), and rms is the stand-off distance to the magnetopause, assuming pressure-balance between the solar wind and the magnetosphere). This is a simple modification of the original Boyle et al. (1997) formulation.

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Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field

Annales Geophysicae ◽

10.5194/angeo-29-31-2011 ◽

2011 ◽

Vol 29 (1) ◽

pp. 31-46 ◽

Cited By ~ 2

Author(s):

S. Baraka ◽

L. Ben-Jaffel

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Interplanetary Magnetic Field ◽

Cell Model ◽

Dynamic Pressure ◽

Outer Boundary ◽

Solar Wind Plasma ◽

Tail Region ◽

Dayside Magnetopause

Abstract. We present a follow up study of the sensitivity of the Earth's magnetosphere to solar wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007), but here during northward Interplanetary Magnetic Field (IMF). The formation of the magnetospheric cavity and its elongation around the planet is obtained with the classical structure of a magnetosphere with parallel lobes. An impulsive disturbance is then applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure followed by its recovery. In response to the imposed drop in the solar wind velocity, a gap (abrupt depression) in the incoming solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE and is comparable to the sizes previously obtained for both Bz<0 and Bz=0. During the initial phase of the disturbance along the x-axis, the dayside magnetopause (MP) expands slower than the previous cases of IMF orientations as a result of the abrupt depression. The size of the MP expands nonlinearly due to strengthening of its outer boundary by the northward IMF. Also, during the initial 100 Δt, the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding, a phenomenon that was also observed for southern IMF conditions but not during the no IMF case. As soon as they felt the solar wind depression, cusps widened at high altitude while dragged in an upright position. For the field's topology, the reconnection between magnetospheric and magnetosheath fields is clearly observed in both the northward and southward cusps areas. Also, the tail region in the northward IMF condition is more confined, in contrast to the fishtail-shape obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE compared to ~103 RE and ~80 RE for Bz=0 and Bz<0, respectively. Our findings are consistent with existing reports from many space observatories (Cluster, Geotail, Themis, etc.) for which predictions are proposed to test furthermore our simulation technique.

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Cluster survey of the mid-altitude cusp: 1. size, location, and dynamics

Annales Geophysicae ◽

10.5194/angeo-24-3011-2006 ◽

2006 ◽

Vol 24 (11) ◽

pp. 3011-3026 ◽

Cited By ~ 26

Author(s):

F. Pitout ◽

C. P. Escoubet ◽

B. Klecker ◽

H. Rème

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Time Delay ◽

Interplanetary Magnetic Field ◽

Statistical Study ◽

Proper Time ◽

Dynamic Pressure ◽

Solar Wind Dynamic Pressure ◽

Summer Hemisphere ◽

External Conditions

Abstract. We present a statistical study of four years of Cluster crossings of the mid-altitude cusp. In this first part of the study, we start by introducing the method we have used a) to define the cusp properties, b) to sort the interplanetary magnetic field (IMF) conditions or behaviors into classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Out of the 920 passes that we have analyzed, only 261 fulfill our criteria and are considered as cusp crossings. We look at the size, location and dynamics of the mid-altitude cusp under various IMF orientations and solar wind conditions. For southward IMF, Bz rules the latitudinal dynamics, whereas By governs the zonal dynamics, confirming previous works. We show that when |By| is larger than |Bz|, the cusp widens and its location decorrelates from By. We interpret this feature in terms of component reconnection occurring under By-dominated IMF. For northward IMF, we demonstrate that the location of the cusp depends primarily upon the solar wind dynamic pressure and upon the Y-component of the IMF. Also, the multipoint capability of Cluster allows us to conclude that the cusp needs typically more than ~20 min to fully adjust its location and size in response to changes in external conditions, and its speed is correlated to variations in the amplitude of IMF-Bz. Indeed, the velocity in °ILAT/min of the cusp appears to be proportional to the variation in Bz in nT: Vcusp=0.024 ΔBz. Finally, we observe differences in the behavior of the cusp in the two hemispheres. Those differences suggest that the cusp moves and widens more freely in the summer hemisphere.

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