The need for accurate measurements of thermal velocity distribution functions in the solar wind

Wilson, L. B.; Goodrich, K.; Turner, D. L.; Cohen, I. J.; Whittlesey, P. L.; Schwartz, Steven J.

doi:10.3389/fspas.2022.1063841

Cited by 14 publications

(17 citation statements)

References 78 publications

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“…However, the dynamics of these components are similar across the shock, so we process them together in the following. This bow shock crossing was reported previously by Hanson et al (2019) (where the measurements in the solar wind were compared with the data from WIND (Wilson et al 2022)) and Lindberg et al (2022). The magnetic field, plasma bulk velocity, and plasma density demonstrate the structure typical for a crossing of a high-Mach number quasi-perpendicular CS.…”

Section: Introductionsupporting

confidence: 81%

Energy Repartition and Entropy Generation across the Earth’s Bow Shock: MMS Observations

Agapitov¹,

Krasnoselskikh²,

Balikhin³

et al. 2023

ApJ

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The evolution of plasma entropy and the process of plasma energy redistribution at the collisionless plasma shock front are evaluated based on the high temporal resolution data from the four Magnetospheric Multiscale spacecraft during the crossing of the terrestrial bow shock. The ion distribution function has been separated into the populations with different characteristic behaviors in the vicinity of the shock: the upstream core population, the reflected ions, the gyrating ions, the ions trapped in the vicinity of the shock, and the downstream core population. The values of ion and electron moments (density, bulk velocity, and temperature) have been determined separately for these populations. It is shown that the solar wind core population bulk velocity slows down mainly in the ramp with the electrostatic potential increase but not in the foot region as it was supposed. The reflected ion population determines the foot region properties, so the proton temperature peak in the foot region is an effect of the relative motion of the different ion populations, rather than an actual increase in the thermal speed of any of the ion population. The ion entropy evaluated showed a significant increase across the shock: the enhancement of the ion entropy occurs in the foot of the shock front and at the ramp, where the reflected ions are emerging in addition to the upstream solar wind ions, the anisotropy growing to generate the bursts of ion-scale electrostatic waves. The entropy of electrons across the shock does not show a significant change: electron heating goes almost adiabatically.

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Section: Introductionsupporting

confidence: 81%

Energy Repartition and Entropy Generation across the Earth’s Bow Shock: MMS Observations

Agapitov¹,

Krasnoselskikh²,

Balikhin³

et al. 2023

ApJ

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“…However, we expect calculating the pressure strain terms in the magnetosheath (high density) to have an excellent signal‐to‐noise ratio. It should, however, be noted that FPI is not designed for the solar wind and is subject to substantial variations at the spacecraft spin frequency (Bandyopadhyay et al., 2018; Roberts et al., 2021; Wilson III et al., 2022); this method should not be used with MMS in the solar wind.…”

Section: Discussionmentioning

confidence: 99%

Estimation of the Error in the Calculation of the Pressure‐Strain Term: Application in the Terrestrial Magnetosphere

et al. 2023

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Calculating the pressure‐strain terms has recently been performed to quantify energy conversion between the bulk flow energy and the internal energy of plasmas. It has been applied to numerical simulations and satellite data from the Magnetospheric MultiScale Mission. The method requires spatial gradients of the velocity and the use of the full pressure tensor. Here we present a derivation of the errors associated with calculating the pressure‐strain terms from multi‐spacecraft measurements and apply it to previously studied examples of magnetic reconnection at the magnetopause and the magnetotail. The errors are small in a dense magnetosheath event but much larger in the more tenuous magnetotail. This is likely due to larger counting statistics in the dense plasma at the magnetopause than in the magnetotail. The propagated errors analyzed in this work are important to understand uncertainties of energy conversion measurements in space plasmas and have applications to current and future multi‐spacecraft missions.This article is protected by copyright. All rights reserved.

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“…The angular and energy resolution of the two instruments is sufficient for direct measurement of resonant energy transfer in velocity space. However, a significant undersampling issue would affect the measurement if the timescale of resonant diffusion is much smaller than the time resolution of the instrument (Verniero et al 2021;Horvath et al 2022;Wilson et al 2022). We also acknowledge that the used angle/energy resolutions in Section 4.3 are simplified to some extent.…”

Section: Discussionmentioning

confidence: 99%

Velocity-space Signatures of Resonant Energy Transfer between Whistler Waves and Electrons in the Earth’s Magnetosheath

Jiang,

Verscharen,

Jeong

et al. 2023

ApJ

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Wave–particle interactions play a crucial role in transferring energy between electromagnetic fields and charged particles in space and astrophysical plasmas. Despite the prevalence of different electromagnetic waves in space, there is still a lack of understanding of fundamental aspects of wave–particle interactions, particularly in terms of energy flow and velocity-space characteristics. In this study, we combine a novel quasilinear model with observations from the Magnetospheric Multiscale mission to reveal the signatures of resonant interactions between electrons and whistler waves in magnetic holes, which are coherent structures often found in the Earth’s magnetosheath. We investigate the energy transfer rates and velocity-space characteristics associated with Landau and cyclotron resonances between electrons and slightly oblique propagating whistler waves. In the case of our observed magnetic hole, the loss of electron kinetic energy primarily contributes to the growth of whistler waves through the n = −1 cyclotron resonance, where n is the order of the resonance expansion in linear Vlasov–Maxwell theory. The excitation of whistler waves leads to a reduction of the temperature anisotropy and parallel heating of the electrons. Our study offers a new and self-consistent understanding of resonant energy transfer in turbulent plasmas.

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The need for accurate measurements of thermal velocity distribution functions in the solar wind

Cited by 14 publications

References 78 publications

Energy Repartition and Entropy Generation across the Earth’s Bow Shock: MMS Observations

Energy Repartition and Entropy Generation across the Earth’s Bow Shock: MMS Observations

Estimation of the Error in the Calculation of the Pressure‐Strain Term: Application in the Terrestrial Magnetosphere

Velocity-space Signatures of Resonant Energy Transfer between Whistler Waves and Electrons in the Earth’s Magnetosheath

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