Detection of Electric-Field Turbulence in the Earth's Bow Shock

Fredricks, R. W.; Kennel, C. F.; Scarf, F. L.; Crook, G. M.; Green, I. M.

doi:10.1103/physrevlett.21.1761

Cited by 106 publications

(37 citation statements)

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“…field strengths for electromagnetic turbulence (20 Hz -4 kHz) occur when the upstream particle de.nsity N ==~ 3 is large and when the shock normal angle w(1,A) is closer to 90°, supporting a previous conclusion that whistler waves comprise the electromag netic turbulence in the bow shock. Electric :fiald turbulence, composed of both electrosta tic and electromag netic fluctuations, correlates with the upstream parameters T IT , T , and *~,a) Fredricks et al [1968Fredricks et al [ , 1970a have shown that electrosta tic turbulence at 1.3 kHz and the scattering of protons correlates ,nth the gradients in the magnetic field at the shock front, thus indicating the presence of a current-dr iven instabilit y. Montgomery et al [1970] and Formisano and Hedgecock [1973a, b] have Rhown that electron thermaliza tion occurs in a thin region upstream of the bow shock, followed by ion thermaliza tion in the main shock transition . Solar "ind ions are reported by Neugebauer [1970] to be substantia lly decelerate d near the upstream side of the bow shock, possibly by a charge separation electric field.…”

Section: mentioning

confidence: 99%

“…It is evident that the average electric field polarizatio n is nearly aligned with the magnetic field vector direction (¢B -¢p ~ 10°); the frequency and average polarizati on therefore identify the noise as electron plasma oscillatio ns [Fredricks et al, 1968[Fredricks et al, , 1970bROdriguez and Gurnett, 1975]. The spectrum of electron plasma oscillation s at about 2219:00 UT (20 seconds before the rapid-samp le data of Figure 14 was obtained) is sharply peaked at the electron plasma frequency near 16.5 kHz.…”

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confidence: 99%

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Correlation of Bow Shock Plasma Wave Turbulence with Solar Wind Parameters

Rodriguez¹,

Gurnett²

1976

J. Geophys. Res.

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The rms field strengths of electrostatic and electromagnetic turbulence in the earth's bow shock, measured in the frequency range 20 Hz to 200 kHz with the Imp 6 satellite, are found to correlate with specific solar wind parameters measured upstream of the bow shock. The largest rms field strengths of electrostatic turbulence (200 Hz to 4 kHz) occur when the upstream electron to proton temperature ratio Te/Tp is large and when the proton temperature Tp is small, an indication that the mechanism for generating electrostatic turbulence in the bow shock is more efficient when lower upstream proton temperatures occur. No substantial correlation is found between the rms field strengths of electrostatic turbulence and three upstream parameters commonly used to classify the magnetohydrodynamic structure of the turbulent bow shock: the Alfvén Mach number MA, the ratio of particle pressure to magnetic field pressure β, and the shock normal angle . The strong correlation with Te/Tp and Tp and the lack of strong correlation with MA,β, and indicate that the strength of electrostatic turbulence in the bow shock is determined by the kinetic properties of the solar wind plasma rather than by its fluid properties. The largest rms field strengths for electromagnetic turbulence (20 Hz to 4 kHz) occur when the upstream particle density N is large and when the shock normal angle is closer to 90°, this result supporting a previous conclusion that whistler waves comprise the electromagnetic turbulence in the bow shock. Electric field turbulence, composed of both electrostatic and electromagnetic fluctuations, correlates with the upstream parameters Te/Tp, Tp, and in such a way as to imply that mode coupling occurs between electrostatic and electromagnetic waves. A broad spectrum of high‐frequency (3–30 kHz) electrostatic turbulence typically observed in the leading edge of the bow shock is interpreted as indicating the region of electron heating. Deeper within the shock transition the intensity of low‐frequency (<3 kHz) electrostatic turbulence greatly increases to form a broad peak, centered between 200 and 800 Hz, and is interpreted as corresponding to the region of maximum proton heating. The characteristic development of the electric field spectrum through the shock transition indicates that strong coupling exists between the electron and proton heating processes.

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Section: mentioning

confidence: 99%

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confidence: 99%

Correlation of Bow Shock Plasma Wave Turbulence with Solar Wind Parameters

Rodriguez¹,

Gurnett²

1976

J. Geophys. Res.

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“…The instability responsible for this noise has been controversial ever since its discovery by Fredricks et al [1968]. The instabilities that could possibly be responsible for this noise are (1) a Buneman mode instability, (2) a current-driven ion-acoustic instability, (3) an ion-beam instability, and (4) an electron-beam instability.…”

Section: A Interpretation Of the High Frequency Electrostatic Noisementioning

confidence: 99%

“…The first observations of magnetic field turbulence associated with the earth's bow shock were obtained by Holzer et al [1966], and the first electric field observations were obtained by Fredricks et al [1968;1970]. Of these the electric field measurements of Fredricks et al are particularly important because they demonstrated that electrostatic turbulence was responsible for the plasma heating and dissipation in the shock.…”

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confidence: 98%

Waves and Instabilities in Collisionless Shocks

Gurnett¹

1984

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“…(a) MHD shock: In space plasmas, electric turbulence, reflected ions, and particle acceleration associated with collisionless Earth's [21][22][23][24][25][26] and Saturn's [27] (MHD) bow shocks have been observed by satellites. From the observation of SNRs, structures of collisionless MHD shock and particle acceleration at the shock front have been studied [28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Collisionless electrostatic shock generation using high-energy laser systems

Sakawa

Morita

Kuramitsu

et al. 2016

Advances in Physics: X

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Collisionless shock is ubiquitous in space and astrophysical plasmas, and is believed to be a source of cosmic rays. In this review article, historical achievements of three different types of collisionless shocks, i.e. magnetohydrodynamic, electromagnetic, and electrostatic (ES) shocks, in theory/simulation, observation in space and astrophysical plasmas, and laboratory experiments are shown. An overview is given on recent progress of collisionless ES shock experiments using high-energy laser systems for two schemes. One is an interaction between laser-produced highdensity ablating plasma and a low-density ambient plasma, and the other is an interaction between laser-ablated counterstreaming plasmas using double-plane target. For the former scheme, detailed measurements of structures of collisionless ES shock and ion-acoustic soliton, and the transition from double-layer to collisionless ES shock are conducted by proton radiography. For the latter scheme, optical diagnostics are used to observe global structures of plasmas and shocks; collective laser Thomson scattering method is applied to clarify local plasma parameters, such as electron and ion temperatures, flow velocity, and electron density; and proton radiography is employed to measure a shock electric field. The measured large density-jump, steepening of self-emission profile, plasma parameters in the upand down-stream regions of a shock, and the narrow width of the shock electric field compared with the ion-ion Coulomb meanfree-path reveal the evidence for the formation of collisionless ES shock. ARTICLE HISTORY

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Detection of Electric-Field Turbulence in the Earth's Bow Shock

Cited by 106 publications

References 5 publications

Correlation of Bow Shock Plasma Wave Turbulence with Solar Wind Parameters

Correlation of Bow Shock Plasma Wave Turbulence with Solar Wind Parameters

Waves and Instabilities in Collisionless Shocks

Collisionless electrostatic shock generation using high-energy laser systems

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