How non-stationary are moderately supercritical shocks?

Gedalin, M.

doi:10.1017/s0022377819000692

Cited by 9 publications

(3 citation statements)

References 59 publications

(118 reference statements)

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“…Using Eqs 3, 7, the Mach number is estimated as M ≈ 3.35, and the ion inertial length corresponds to the duration ≈ 6.0 s. Using the distance between the two adjacent downstream maxima gives a result that is inconsistent with other estimates. Using twice this distance [48,49], together with the foot length, also gives M ≈ 3.35. Note that the precision of the determination of the durations used for the estimates and the application of the wavelet transform is not sufficient to ensure the above excellent agreement of the Mach number estimates.…”

Section: Figure 10 |mentioning

confidence: 98%

“…The decay is faster for higher upstream ion temperatures [45]. If the effect of reflected ions is significant, other peaks/dips may exist between the main maxima/minima [48,49]. In this case, Δ would correspond to the distance between a maximum and the next second maximum, or approximately the twice distance between two adjacent maxima.…”

Section: Downstream Magnetic Oscillationsmentioning

confidence: 99%

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Theory Helps Observations: Determination of the Shock Mach Number and Scales From Magnetic Measurements

et al. 2022

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The Mach number is one of the key parameters of collisionless shocks. Understanding shock physics requires knowledge of the spatial scales in the shock transition layer. The standard methods of determining the Mach number and the spatial scales require simultaneous measurements of the magnetic field and the particle density, velocity, and temperature. While magnetic field measurements are usually of high quality and resolution, particle measurements are often either unavailable or not properly adjusted to the plasma conditions. We show that theoretical arguments can be used to overcome the limitations of observations and determine the Mach number and spatial scales of the low-Mach number shock when only magnetic field data are available.

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Section: Figure 10 |mentioning

confidence: 98%

Section: Downstream Magnetic Oscillationsmentioning

confidence: 99%

Theory Helps Observations: Determination of the Shock Mach Number and Scales From Magnetic Measurements

et al. 2022

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“…In the hybrid model ions are modeled as large ensemble of particles embedded in the magnetic field and electrons are fluid. Previous models focused primarily on electron‐proton plasma (e.g., Burgess & Scholer, 2015; Burgess et al., 2016; Ofman & Gedalin, 2013a), while recently the models were extended by adding α particles in particle trajectory tracing model (Gedalin, 2017a, 2017b), in nonlinear one‐dimensional (1D) hybrid models (Gedalin, 2019a, 2019b; Gedalin et al., 2018) and in 2.5D hybrid models of quasi‐perpendicular shocks (Hao et al., 2014; Ofman et al., 2019; Preisser et al., 2020). Observations of surface irregularities of high‐ M interplanetary shocks at ion scales were reported (e.g., Wilson et al., 2017; Kajdič et al., 2019), and supplemented by two‐dimensional (2D) hybrid modeling of the e − p shock plasma.…”

Section: Introductionmentioning

confidence: 99%

Oblique High Mach Number Heliospheric Shocks: The Role of α Particles

et al. 2021

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Introduction and MotivationMagnetized, collisionless shocks are ubiquitous phenomena in the heliosphere and in astrophysical plasma. Oblique or quasi-perpendicular interplanetary shocks are associated with the most energetic Coronal Mass Ejections (CMEs) and have super-Alfvénic speeds (e.g., Bale et al., 2005;Krasnoselskikh et al., 2013), with high Mach number shocks potentially most geoeffective. The Wind spacecraft, launched in 1994, provides continuous solar wind measurements on a halo orbit around the L1 Lagrange point (the distance of about 0.01 AU from the Earth toward the Sun where the spacecraft's motion around the Sun matches that of the Earth), that include magnetic field vector, and plasma properties. The Deep Space Climate Observatory (DSCOVR), launched in 2015, also around L1, in addition to Earth observing instruments, carries the Plasma-Magnetometer instruments that provides high-cadence magnetic field and plasma in-situ data. Due to their strategic location near L1, the satellites provide early warning for solar activity that propagates toward the Earth, and ample detailed heliospheric shock data. However, these single-point observations cannot provide the complete picture of the multi-dimensional multi-ion shock structure and dynamics-a gap that can be possibly filled by numerical modeling.High Mach number M (where M indicates the fast magnetosonic speed Mach number) shocks in heliospheric plasma such as the solar wind (SW) and Earths' magnetosphere were modeled with 2.5D hybrid models in the past in order to investigate ion-kinetic properties of these shocks. In the hybrid model ions are modeled as large ensemble of particles embedded in the magnetic field and electrons are fluid. Previous models focused primarily on electron-proton plasma (e.g.,

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Electron scattering on small-scale electrostatic fields in the shock front

Gedalin

2024

J. Plasma Phys.

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Electron heating and acceleration in collisionless shocks is a long-standing problem. Rapid isotropization of heated electrons cannot be explained solely by the cross-shock potential. In addition, the macroscopic cross-shock potential prevents efficient reflection and injection into the diffusive acceleration regime. Recent observations have shown that small-scale electric fields are present in the shock front, together with the large-scale cross-shock potential. These small-scale fields have been found also in the upstream and downstream regions. Electron heating in shocks is produced by the combined action of the large- and small-scale fields. The large-scale potential determines the energy transferred to the electrons. The small-scale electrostatic fields scatter electrons. Here we study the scattering of electrons on the typical waveforms, namely solitary bipolar spikes and wavepackets. The main effect is the generation of backstreaming electrons with large pitch angles. It is found that wavepackets are more efficient in electron reflection in the interaction of electrons both with a single spike and with multiple spikes.

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How non-stationary are moderately supercritical shocks?

Cited by 9 publications

References 59 publications

Theory Helps Observations: Determination of the Shock Mach Number and Scales From Magnetic Measurements

Theory Helps Observations: Determination of the Shock Mach Number and Scales From Magnetic Measurements

Oblique High Mach Number Heliospheric Shocks: The Role of α Particles

Electron scattering on small-scale electrostatic fields in the shock front

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