The thickness of the magnetosheath: Constraints on the polytropic index

Farris, M. H.; Petrinec, S. M.; Russell, C. T.

doi:10.1029/91gl02090

Cited by 163 publications

(229 citation statements)

References 12 publications

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“…The computations based on Slavin and Holzer (1981); Farris et al (1991) led to similar results. The horizontal dashed line corresponds to the critical value of θ c Bn =39.9 • .…”

Section: Local Bow Shock Geometrysupporting

confidence: 68%

“…Another model by Cairns et al (1995) emphasizes the MHD effects at low Mach numbers. Finally, a gas dynamics-based model using 351 independent bow shock crossings by the ISEE-1 spacecraft has been reported by Farris et al (1991). They found that these data fit a hyperboloid shape well.…”

Section: Shock Geometrymentioning

confidence: 99%

“…They found that these data fit a hyperboloid shape well. For comparison purposes, we use the Farris et al (1991), Cairns et al (1995), and Slavin and Holzer (1981) models. We do not use the recent Peredo et al (1995) model because it has been shown to overestimate the bow shock stand-off position by as much as 20% (Merka et al, 2003).…”

Section: Shock Geometrymentioning

confidence: 99%

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Bow shock specularly reflected ions in the presence of low-frequency electromagnetic waves: a case study

et al. 2004

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Abstract. An energetic ion (E≤40 keV) event observed by the CLUSTER/CIS experiment upstream of the Earth's bow shock is studied in detail. The ion event is observed in association with quasi-monochromatic ULF MHD-like waves, which we show modulate the ion fluxes. According to three statistical bow shock position models, the Cluster spacecrafts are located at ∼0.5 R E from the shock and the averaged bow shock θ Bn0 is about ∼30 • . The analysis of the threedimensional angular distribution indicates that ions propagating roughly along the magnetic field direction are observed at the onset of the event. Later on, the angular distribution is gyrophase-bunched and the pitch-angle distribution is peaked at α 0 ∼θ Bn0 , consistent with the specular reflection production mechanism. The analysis of the waves shows that they are left-handed in the spacecraft frame of reference (right-handed in the solar wind frame) and propagate roughly along the ambient magnetic field; we have found that they are in cyclotron-resonance with the field-aligned beam observed just upstream. Using properties of the waves and particles, we explain the observed particle flux-modulation in the context of θ Bn changes at the shock caused by the convected ULF waves. We have found that the high count rates coincide with particles leaving the shock when θ Bn angles are less than ∼40 • , consistent with the specular reflection hypothesis as the production mechanism of ions.

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“…The computations based on Slavin and Holzer (1981); Farris et al (1991) led to similar results. The horizontal dashed line corresponds to the critical value of θ c Bn =39.9 • .…”

Section: Local Bow Shock Geometrysupporting

confidence: 68%

Section: Shock Geometrymentioning

confidence: 99%

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Bow shock specularly reflected ions in the presence of low-frequency electromagnetic waves: a case study

et al. 2004

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“…The different orientation of IMF can affect the fast magnetosonic Mach number. If the waves at the nose of the magnetopause propagate in the radial direction, their fast magnetosonic Mach number will increase under the radial IMF condition, and consequently reducing the standoff distance of the bow shock and then the thickness of the magnetosheath [Farris et al, 1991]. For this reason, MHD modelers should use actual solar wind conditions in global simulations of radial IMF events.…”

Section: Discussionmentioning

confidence: 99%

A reexamination of long‐duration radial IMF events

Shue

Chao

et al. 2014

JGR Space Physics

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The radial interplanetary magnetic field (IMF) is one of the special solar wind conditions when the orientation of the IMF is aligned with the solar wind velocity. In this study, we reexamine the solar wind condition during the long-duration radial IMF (>4 h) using the OMNI solar wind data. During the events, the IMF magnitude, solar wind speed, density, and especially its temperature are depressed in comparison with their yearly averages. In contrast to previous studies, we have found that the total time of the radial IMF per year does not change with solar activity. MHD simulation models failed to predict the location of the magnetopause under the radial IMF condition. A part of the inaccuracy is due to the use of assumed solar wind parameters in the simulations. Here we provide MHD modelers with the real solar wind parameters for simulations of the radial IMF.

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“…The preceding parameters resulted in an estimation of Alfvén Mach number of M a = 3.7. The Farris shock model surface (Farris et al, 1991) was used to determine the shock normal direction ofn = [0.99, 0.09, −0.03]. The projection of the magnetic field alongn can be seen in the top panel of Fig.…”

Section: Datasets and Instrumentationmentioning

confidence: 99%

Dispersion of low frequency plasma waves upstream of the quasi-perpendicular terrestrial bow shock

et al. 2013

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Low frequency waves in the foot of a supercritical quasi-perpendicular shock front have been observed since the very early in situ observations of the terrestrial bow shock (Guha et al., 1972). The great attention that has been devoted to these type of waves since the first observations is explained by the key role attributed to them in the processes of energy redistribution in the shock front by various theoretical models. In some models, these waves play the role of the intermediator between the ions and electrons. It is assumed that they are generated by plasma instability that exist due to the counter-streaming flows of incident and reflected ions. In the second type of models, these waves result from the evolution of the shock front itself in the quasi-periodic process of steepening and overturning of the magnetic ramp. However, the range of the observed frequencies in the spacecraft frame are not enough to distinguish the origin of the observed waves. It also requires the determination of the wave vectors and the plasma frame frequencies. Multipoint measurements within the wave coherence length are needed for an ambiguous determination of the wave vectors. In the main multi-point missions such as ISEE, AMPTE, Cluster and THEMIS, the spacecraft separation is too large for such a wave vector determination and therefore only very few case studies are published (mainly for AMPTE UKS AMPTE IRM pair). Here we present the observations of upstream low frequency waves by the Cluster spacecraft which took place on 19 February 2002. The spacecraft separation during the crossing of the bow shock was small enough to determine the wave vectors and allowed the identification of the plasma wave dispersion relation for the observed waves. Presented results are compared with whistler wave dispersion and it is shown that contrary to previous studies based on the AMPTE data, the phase velocity in the shock frame is directed downstream. The consequences of this finding for both types of models that were developed to explain the generation of these waves are discussed

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The thickness of the magnetosheath: Constraints on the polytropic index

Cited by 163 publications

References 12 publications

Bow shock specularly reflected ions in the presence of low-frequency electromagnetic waves: a case study

Bow shock specularly reflected ions in the presence of low-frequency electromagnetic waves: a case study

A reexamination of long‐duration radial IMF events

Dispersion of low frequency plasma waves upstream of the quasi-perpendicular terrestrial bow shock

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