Precision Electron Measurements in the Solar Wind at 1 au from NASA's Wind Spacecraft

Abstract

This work aims to characterize precisely and systematically the non-thermal characteristics of the electron Velocity Distribution Function (eVDF) in the solar wind at 1 au using data from the Wind spacecraft. We present a comprehensive statistical analysis of solar wind electrons at 1 au using the electron analyzers of the 3D-Plasma instrument on board Wind. This work uses a sophisticated algorithm developed to analyze and characterize separately the three populations - core, halo and strahl - of the eVDF up to 2 keV. The eVDF data are calibrated using independent electron parameters obtained from the quasi-thermal noise around the electron plasma frequency measured by the Thermal Noise Receiver. The code determines the respective set of total electron, core, halo and strahl parameters through non-linear least-square fits to the measured eVDF, taking properly into account spacecraft charging and other instrumental effects. We use four years, ~ 280000 independent measurements of core, halo and strahl parameters to investigate the statistical properties of these different populations in the solar wind. We discuss the distributions of their respective densities, drift velocities, temperature, and temperature anisotropies as functions of solar wind speed. We also show distributions with solar wind speed of the total density, temperature, temperature anisotropy and heat flux, as well as those of the proton temperature, proton-to-electron temperature ratio, proton and electron beta. Intercorrelations between some of these parameters are also discussed. The present dataset represents the largest, high-precision, collection of electron measurements in the pristine solar wind at 1~AU. It provides a new wealth of information on electron microphysics. Its large volume will enable future statistical studies of parameter combinations and their dependencies under different plasma conditions.

total of 21 pages, 17 figures, 1 appendix and 7 tables

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• Whistler wave occurrence and the interaction with strahl electrons during the first encounter of Parker Solar Probe
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• Parker Solar Probe evidence for scattering of electrons in the young solar wind by narrowband whistler-mode waves
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Cited by in corpus (9)

• Triggered ion acoustic waves in the solar wind
• The Stability of the Electron Strahl against the Oblique Fast-magnetosonic/Whistler Instability in the Inner Heliosphere
• Whistler waves in the young solar wind: statistics of amplitude and propagation direction from Parker Solar Probe Encounters 1-11
• A Kinetic Model of Solar Wind Acceleration Driven by Ambipolar Electric Potential and Velocity-Space Diffusion
• Particle-In-Cell Simulations of Sunward and Anti-sunward Whistler Waves in the Solar Wind
• Electron Heat Flux and Whistler Instability in the Earth's Magnetosheath
• Transport of electrons in tangled magnetic fields
• Formation of Suprathermal Electron Populations in the Expanding, Turbulent Solar Wind
• Unified Description of Kappa-type velocity distributions