Quasi‐thermal noise spectroscopy: The art and the practice

Meyer‐Vernet, N.; Issautier, Karine; Moncuquet, M.

doi:10.1002/2017ja024449

Cited by 84 publications

(77 citation statements)

References 85 publications

(157 reference statements)

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“…The distinguishing feature of QTN spectroscopy is that the antenna response function is factored into the standard electrostatic field fluctuation spectrum computed on the basis of thermal spontaneous emission theory, so that the resulting formula corresponds to the actual antenna potential. In specific, the voltage power spectrum of the antenna,

V_{ω}^{2}

, is given by the convolution of spontaneously emitted electrostatic fluctuations,

{⟨ δ E^{2} ⟩}_{boldk, ω}

, and antenna response factor, F ( k ) (Meyer & Vernet, ; Meyer‐Vernet et al, ),

\begin{matrix} right V_{ω}^{2} & left = 2 \int \frac{{normald}^{3} k}{k^{2}} F (k) {⟨ δ E^{2} ⟩}_{k, ω}, & right \\ right F (k) & left = {|\frac{4 \sin (k_{false‖} L / 2)}{k_{false‖} L} J_{0} (k_{⊥} a)|}^{2}, \end{matrix}

where quasi stationary plasma frame is assumed. Here, k ⊥ and k ‖ are wave vector components perpendicular and parallel with respect to the linear antenna, respectively, and a is the antenna radius.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Quasi Thermal Noise Spectroscopy for Van Allen Probes

et al. 2019

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Quasi thermal fluctuations in the Langmuir/upper-hybrid frequency range are pervasively observed in space plasmas including the radiation belt and the ring current region of inner magnetosphere as well as the solar wind. The quasi thermal noise spectroscopy may be employed in order to determine the electron density and temperature as well as to diagnose the properties of energetic electrons when direct measurements are not available. However, when employing the technique, one must carefully take the spacecraft orientation into account. The present paper takes the upper-hybrid and multiple harmonic-or (n + 1∕2)f ce -emissions measured by the Van Allen Probes as an example in order to illustrate how the spacecraft antenna geometrical factor can be incorporated into the theoretical interpretation. This method can in principle be applied to other spacecraft, including the Parker Solar Probe.

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V_{ω}^{2}

, is given by the convolution of spontaneously emitted electrostatic fluctuations,

{⟨ δ E^{2} ⟩}_{boldk, ω}

, and antenna response factor, F ( k ) (Meyer & Vernet, ; Meyer‐Vernet et al, ),

\begin{matrix} right V_{ω}^{2} & left = 2 \int \frac{{normald}^{3} k}{k^{2}} F (k) {⟨ δ E^{2} ⟩}_{k, ω}, & right \\ right F (k) & left = {|\frac{4 \sin (k_{false‖} L / 2)}{k_{false‖} L} J_{0} (k_{⊥} a)|}^{2}, \end{matrix}

Section: Theoretical Considerationsmentioning

confidence: 99%

Quasi Thermal Noise Spectroscopy for Van Allen Probes

et al. 2019

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“…Introduced onboard ISEE 3 (Meyer-Vernet 1979), and pioneered to measure the cold (Meyer-Vernet et al 1986a) and hot (Meyer-Vernet et al 1986b) electrons in the tail of a comet, it uses the power spectrum of the voltage induced on an electric antenna by the particle quasi-thermal motions, measured by a radio receiver connected to an electric antenna. The signature of the electrons is a line at the electron plasma frequency f p , which reveals the total electron density n ∝ f 2 p , whereas the shape of the line reveals the electron kinetic temperature, as well as its thermal (core) and suprathermal components (Meyer-Vernet et al (2017) and references therein).…”

mentioning

confidence: 99%

First In Situ Measurements of Electron Density and Temperature from Quasi-thermal Noise Spectroscopy with Parker Solar Probe/FIELDS

Moncuquet¹,

Meyer‐Vernet²,

Issautier³

et al. 2020

ApJS

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130

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Heat transport in the solar corona and wind is still a major unsolved astrophysical problem. Because of the key role played by electrons, the electron density and temperature(s) are important prerequisites for understanding these plasmas. We present such in situ measurements along the two first solar encounters of Parker Solar Probe (PSP), between 0.5 and 0.17 AU from the Sun, revealing different states of the emerging solar wind near solar activity minimum. These preliminary results are obtained from a simplified analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the Radio Frequency Spectrometer (RFS/FIELDS). The local electron density is deduced from the tracking of the plasma line, which enables accurate measurements, independent of calibrations and spacecraft perturbations, whereas the temperatures of the thermal and supra-thermal components of the velocity distribution, as well as the average kinetic temperature are deduced from the shape of the plasma line. The temperature of the weakly collisional thermal population, similar for both encounters, decreases with distance as R −0.74 , much slower than adiabatic. In contrast, the temperature of the nearly collisionless suprathermal population exhibits a virtually flat radial 2 Moncuquet et al.variation. The 7-second resolution of the density measurements enables us to deduce the low-frequency spectrum of compressive fluctuations around perihelion, varying as f −1.4 . This is the first time that QTN spectroscopy is implemented with an electric antenna length not exceeding the plasma Debye length. As PSP will approach the Sun, the decrease in Debye length is expected to considerably improve the accuracy of the temperature measurements.

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“…According to equations and the electric and magnetic fluctuations are given by 〈 δ E 2 〉 k , ω and 〈 δ B 2 〉 k , ω . According to Meyer‐Vernet et al (), the electric field measured by the antenna characterized by the current distribution J k in Fourier space, immersed in a plasma drifting with velocity V , measures the voltage power at the antenna at frequency f , which is related to the spontaneously emitted electric field fluctuations via

V_{f}^{2} = \frac{2}{{false(2 π false)}^{3}} \int normald boldk \frac{false| boldk \cdot J_{k} false|}{k^{2}} {〈 δ E^{2} 〉}_{boldk, ω - boldk \cdot boldV} .

Meyer‐Vernet et al () subsequently discusse various antenna geometries including the linear boom electric field antenna, unequal booms, and fat and biased antenna. Such considerations lead to various functional forms for J k .…”

Section: Discussionmentioning

confidence: 99%

“…According to equations (1) and (2) the electric and magnetic fluctuations are given by ⟨ E 2 ⟩ k, and ⟨ B 2 ⟩ k, . According to Meyer-Vernet et al (2017), the electric field measured by the antenna characterized by the current distribution J k in Fourier space, immersed in a plasma drifting with velocity V, measures the voltage power at the antenna at frequency f , which is related to the spontaneously emitted electric field fluctuations via…”

Section: Discussionmentioning

confidence: 99%

“…The purpose of this paper is to address this problem in a quantitative manner and to calculate the predicted level of electric versus magnetic field fluctuation intensities. By employing the data‐theory comparison analysis as recently carried out by Hwang et al (), who assumed electrostatic formalism, we make a quantitative prediction on the expected level of the magnetic field intensity spectrum that, when combined with the antenna geometric factor (Meyer‐Vernet et al, ), may be used as a tool for electromagnetic quasi‐thermal spectroscopy. The potential significance of the present findings in broader astrophysical contexts will also be discussed.…”

Section: Introductionmentioning

confidence: 99%

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Electromagnetic Thermal Noise in Upper‐Hybrid Frequency Range

et al. 2018

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The inner magnetosphere including the radiation belt and ring current environment is replete with high‐frequency fluctuations with peak intensity occurring near upper‐hybrid frequency and/or multiple harmonic electron cyclotron frequencies above and below the upper‐hybrid frequency. Past and contemporary spacecraft missions, including the Van Allen Probes, were designed to detect the electric field spectrum only for these high‐frequency fluctuations. Making use of the recently formulated generalized theory of electromagnetic spontaneous emission in thermal magnetized plasmas, it is shown that upper‐hybrid/multiple harmonic electron cyclotron emissions are characterized by a significant magnetic field component, even in the high‐frequency regime. Such a prediction may potentially be tested by upcoming spacecraft missions including the Solar Probe Orbiter and Parker Solar Probe. The present finding may also have a potentially significant ramification for the broader astrophysical contexts.

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Quasi‐thermal noise spectroscopy: The art and the practice

Cited by 84 publications

References 85 publications

Quasi Thermal Noise Spectroscopy for Van Allen Probes

Quasi Thermal Noise Spectroscopy for Van Allen Probes

First In Situ Measurements of Electron Density and Temperature from Quasi-thermal Noise Spectroscopy with Parker Solar Probe/FIELDS

Electromagnetic Thermal Noise in Upper‐Hybrid Frequency Range

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