Electron heat flux in the near-Sun environment

Abstract

We survey the electron heat flux observed by the Parker Solar Probe (PSP) in the near-Sun environment at heliocentric distances of 0.125-0.25 AU. We utilized measurements from the Solar Wind Electrons Alphas and Protons and FIELDS experiments to compute the solar wind electron heat flux and its components and to place these in context. The PSP observations reveal a number of trends in the electron heat flux signatures near the Sun. The magnitude of the heat flux is anticorrelated with solar wind speed, likely as a result of the lower saturation heat flux in the higher-speed wind. When divided by the saturation heat flux, the resulting normalized net heat flux is anticorrelated with plasma beta on all PSP orbits, which is consistent with the operation of collisionless heat flux regulation mechanisms. The net heat flux also decreases in very high beta regions in the vicinity of the heliospheric current sheet, but in most cases of this type the omnidirectional suprathermal electron flux remains at a comparable level or even increases, seemingly inconsistent with disconnection from the Sun. The measured heat flux values appear inconsistent with regulation primarily by collisional mechanisms near the Sun. Instead, the observed heat flux dependence on plasma beta and the distribution of suprathermal electron parameters are both consistent with theoretical instability thresholds associated with oblique whistler and magnetosonic modes.

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Cited by in corpus (28)

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• On the role of solar wind expansion as a source of whistler waves: scattering of suprathermal electrons and heat flux regulation in the inner heliosphere
• Whistler waves observed by Solar Orbiter / RPW between 0.5 AU and 1 AU
• Parker Solar Probe evidence for scattering of electrons in the young solar wind by narrowband whistler-mode waves
• Quantifying the Energy Budget in the Solar Wind from 13.3-100 Solar Radii
• Solar wind energy flux observations in the inner heliosphere: First results from Parker Solar Probe
• Generalized Fluid Models of the Braginskii Type
• Narrowband oblique whistler-mode waves: Comparing properties observed by Parker Solar Probe at <0.2 AU and STEREO at 1 AU
• Modeling interactions of narrowband large amplitude whistler-mode waves with electrons in the solar wind inside ~.3 AU and at 1 AU using a particle tracing code
• Parker Solar Probe Observations of High Plasma Beta Solar Wind from Streamer Belt
• Total Electron Temperature Derived from Quasi-Thermal Noise Spectroscopy In the Pristine Solar Wind: Parker Solar Probe Observations
• Thermal energy budget of electrons in the inner heliosphere: Parker Solar Probe Observations
• The Stability of the Electron Strahl against the Oblique Fast-magnetosonic/Whistler Instability in the Inner Heliosphere
• Electron Heat Flux in the Solar Wind: Generalized Approaches to Fluid Transport with a Variety of Skewed Velocity Distributions
• Collisionless conduction in a high-beta plasma: a collision operator for whistler turbulence
• Quantifying the diffusion of suprathermal electrons by whistler waves between 0.2 and 1 AU with Solar Orbiter and Parker Solar Probe
• The Kinetic Expansion of Solar-Wind Electrons: Transport Theory and Predictions for the very Inner Heliosphere
• Stochastic diffusion of electrons interacting with whistler-mode waves in the solar wind
• Reconstruction of Polarization Properties of Whistler Waves From Two Magnetic and Two Electric Field Components: Application to Parker Solar Probe Measurements
• Particle-In-Cell Simulations of Sunward and Anti-sunward Whistler Waves in the Solar Wind
• Quasi-parallel anti-sunward propagating whistler waves associated to the electron-deficit in the near-Sun solar wind: Particle-in-Cell simulation
• Electron Heat Flux and Whistler Instability in the Earth's Magnetosheath
• Parker Solar Probe evidence for the absence of whistlers close to the Sun to scatter strahl and regulate heat flux
• Transport of electrons in tangled magnetic fields
• The Quiet-Sun DEM Under Kappa: Diagnostic Degeneracy and the Failure of the Conductive Closure
• Ambipolar electric field and potential in the solar wind estimated from electron velocity distribution functions