Distribution of escaping ions produced by non‐specular reflection at the stationary quasi‐perpendicular shock front

Gedalin, M.; Liverts, M.; Balikhin, M. A.

doi:10.1029/2007ja012894

Cited by 19 publications

(20 citation statements)

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“…They have shown that all these populations were produced by ion gyration and reflection at the shock front. This finding was later supported by theoretical studies [ Gedalin et al , ]. Oka et al [] suggested that backstreaming ions are produced by multiple interaction of the incident ions with the supercritical shock transition.…”

Section: Introductionmentioning

confidence: 73%

“…It was shown, however, that such specular reflection requires too high cross‐shock potentials [ Wilkinson and Schwartz , ] and that at low initial temperatures the reflection occurs behind the ramp due to the gyration in the increased magnetic field [ Gedalin , ]. At higher temperatures, some of the incident ions were shown to be reflected at low Mach numbers and low magnetic compressions [ Gedalin et al , ]. Most incident ions are directly transmitted downstream upon crossing the ramp.…”

Section: Introductionmentioning

confidence: 99%

“…Ion transmission in such shocks for low β of incident ions has been extensively studied in the last several years. In particular, it has been shown that gyration and gradual gyrophase mixing of the downstream distribution of transmitted ions is responsible for the downstream coherent oscillations of the magnetic field strength [ Balikhin et al , ; Gedalin et al , ; Ofman et al , ; Gedalin et al , ; Gedalin , ]. Ion reflection at such shocks has not been devoted sufficient attention so far.…”

Section: Introductionmentioning

confidence: 99%

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Transmitted, reflected, quasi‐reflected, and multiply reflected ions in low‐Mach number shocks

Gedalin

2016

JGR Space Physics

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The dependence of ion dynamics on the cross‐shock potential and upstream βi in low‐Mach number marginally critical shocks is studied using advanced test particle analysis,. The directly transmitted ions provide the main contribution to the downstream ion pressure. The fraction of reflected ions increases with the increase of the cross‐shock potential and βi. This fraction is small and their contribution to the downstream ion pressure is negligible in marginally critical shocks. A population of quasi‐reflected ions is identified. These ions make a loop inside the ramp and do not appear upstream. They acquire energies comparable to the energies of the true reflected ions, are observed as a halo in the downstream ion distribution, and contribute significantly to the downstream pressure. Thus, the transmitted and quasi‐reflected ions shape the downstream magnetic profile. At higher cross‐shock potentials and βi the reflected ions cause formation of a magnetic dip just ahead of the ramp. A small fraction of ions are multiply reflected at the shock front. All these ions escape into the upstream region and all escaping ions are mutliply reflected.

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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transmitted, reflected, quasi‐reflected, and multiply reflected ions in low‐Mach number shocks

Gedalin

2016

JGR Space Physics

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“…A possible reason for the decrease in normalized potential with increasing M A is that the increase in cross‐shock potential may prove too strong to allow ion reflection [ Wilkinson and Schwartz , 1990] and so reduce the number and energy of the directly transmitted ions [ Gedalin , 1996a]. However, the number of ions escaping would be expected to increase with increasing Mach number [ Gedalin et al , 2008], to provide the required dissipation to prevent overturning.…”

Section: Discussionmentioning

confidence: 99%

A statistical study of the cross‐shock electric potential at low Mach number, quasi‐perpendicular bow shock crossings using Cluster data

Dimmock¹,

Balikhin²,

Krasnoselskikh³

et al. 2012

J. Geophys. Res.

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.[1] The cross-shock electrostatic potential at the front of collision-less shocks plays a key role in the distribution of energy at the shock front. Multipoint measurements such as those provided by the Cluster II mission provide an ideal framework for the study of the cross-shock potential because of their ability to distinguish between temporal and spacial variations at the shock front. We present a statistical study of the cross-shock potential calculated for around 50 crossings of the terrestrial bow shock. The statistical dependency of the normalized (with resect to upstream ion kinetic energy) cross-shock potential (F K ) on the upstream Alfvén Mach number is in good agreement with analytical results that predict decrease of F k with increasing Mach number.Citation: Dimmock, A. P., M. A. Balikhin, V. V. Krasnoselskikh, S. N. Walker, S. D. Bale, and Y. Hobara (2012), A statistical study of the cross-shock electric potential at low Mach number, quasi-perpendicular bow shock crossings using Cluster data,

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“…Field‐aligned beams are generally seen upstream of Earth's bow shock where 40° ≤

θ_{B_{N}}

≤ 70° [see, for example, Paschmann et al ., ]. A number of works have studied the mechanisms by which ions can escape upstream of quasi‐perpendicular shocks [see, for example, Burgess , ; Gedalin et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Interplanetary shocks and foreshocks observed by STEREO during 2007–2010

et al. 2016

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Interplanetary shocks in the heliosphere modify the solar wind through which they pass. In particular, shocks play an important role in particle acceleration. During the extended solar minimum (2007–2010) STEREO observed 65 forward shocks driven by stream interactions (SI), with magnetosonic Mach numbers Mms ≈ 1.1–4.0 and shock normal angles θBN ~ 20–87°. We analyze the waves associated with these shocks and find that the region upstream can be permeated by whistler waves (f ~ 1 Hz) and/or ultra low frequency (ULF) waves (f ~ 10−2–10−1 Hz). While whistlers appear to be generated at the shock, the origin of ULF waves is most probably associated with local kinetic ion instabilities. We find that when the Mach number (Mms) is low and the shock is quasi‐perpendicular ( θBN > 45°) whistler waves remain close to the shock. As Mms increases, the shock profile changes and can develop a foot and overshoot associated with ion reflection and gyration. Whistler precursors can be superposed on the foot region, so that some quasi‐perpendicular shocks have characteristics of both subcritical and supercritical shocks. When the shock is quasi‐parallel ( θBN < 45°) a large foreshock with suprathermal ions and waves can form. Upstream, there are whistler trains at higher frequencies whose characteristics can be slightly modified probably by reflected and/or leaked ions and by almost circularly polarized waves at lower frequencies that may be locally generated by ion instabilities. In contrast with planetary bow shocks, most of the upstream waves studied here are mainly transverse and no steepening occurs. Some quasi‐perpendicular shocks (45° < θBN < 60°) are preceded by ULF waves and ion foreshocks. Fluctuations downstream of quasi‐parallel shocks tend to have larger amplitudes than waves in the sheath of quasi‐perpendicular shocks. We compare SI‐driven shock properties with those of shocks generated by interplanetary coronal mass ejections (ICMEs). During the same years, STEREO observed 20 ICME‐driven shocks with Mms ≈ 1.2–4.0 and θBN ~ 38–85°. We find that shocks driven by ICMEs tend to have larger proton foreshocks (dr ~ 0.1 AU) than shocks driven by stream interactions (dr ≤ 0.05 AU). This difference of ion foreshock size should be linked to shock age: ICME‐driven shocks form at shorter distances to the Sun and therefore can energize particles for longer times as they propagate to 1 AU, while stream interaction shocks form closer to Earth's orbit and have been accelerating ions for a shorter interval of time.

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Distribution of escaping ions produced by non‐specular reflection at the stationary quasi‐perpendicular shock front

Cited by 19 publications

References 60 publications

Transmitted, reflected, quasi‐reflected, and multiply reflected ions in low‐Mach number shocks

Transmitted, reflected, quasi‐reflected, and multiply reflected ions in low‐Mach number shocks

A statistical study of the cross‐shock electric potential at low Mach number, quasi‐perpendicular bow shock crossings using Cluster data

Interplanetary shocks and foreshocks observed by STEREO during 2007–2010

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