Numerical Modeling of Electron Transport in Solar Wind: Effects of Whistler Turbulence and Coulomb Collisions

<div>Simulation results from a global magnetohydrodynamic model of the solar corona and the solar wind are compared with Parker Solar Probe's (PSP) observations during its first several orbits. The fully three-dimensional model (Usmanov et al., 2018, ApJ, 865, 25) is based on Reynolds-averaged mean-flow equations coupled with turbulence transport equations. The model accounts for effects of electron heat conduction, Coulomb collisions, Reynolds stresses, and heating of protons and electrons via nonlinear turbulent cascade. Turbulence transport equations for turbulence energy, cross helicity, and correlation length are solved concurrently with the mean-flow equations. We specify boundary conditions at the coronal base using solar synoptic magnetograms and calculate plasma, magnetic field, and turbulence parameters along the PSP trajectory. We also accumulate data from all orbits considered, to obtain the trends observed as a function of heliocentric distance. Comparison of simulation results with PSP data show general agreement. Finally, we generate synthetic fluctuations constrained by the local rms turbulence amplitude given by the model, and compare properties of this synthetic turbulence with PSP observations.</div>

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Proton Beam Abundance Variations and Their Relation to Alpha Particle Properties

The Astrophysical Journal ◽

10.3847/1538-4357/ac2c03 ◽

2021 ◽

Vol 923 (2) ◽

pp. 170

Author(s):

Tereza Ďurovcová ◽

Jana Šafránková ◽

Zdeněk Němeček

Keyword(s):

Solar Wind ◽

Proton Beam ◽

Alpha Particle ◽

Source Region ◽

Radial Distance ◽

Alpha Particles ◽

Momentum Balance ◽

Particle Interactions ◽

Coulomb Collisions ◽

Particle Properties

Abstract Less abundant but still dynamically important solar wind components are the proton beam and alpha particles, which usually contribute similarly to the total ion momentum. The main characteristics of alpha particles are determined by the solar wind source region, but the origin of the proton beam and its properties are still not fully explained. We use the plasma data measured in situ on the path from 0.3 to 1 au (Helios 1 and 2) and focus on the proton beam development with an increasing radial distance as well as on the connection between the proton beam and alpha particle properties. We found that the proton beam relative abundance increases with increasing distance from the Sun in the collisionally young streams. Among the mechanisms suggested for beam creation, we have identified the wave–particle interactions with obliquely propagating Alfvén modes being consistent with observations. As the solar wind streams get collisionally older, the proton beam decay gradually dominates and the beam abundance is reduced. In search for responsible mechanisms, we found that the content of alpha particles is correlated with the proton beam abundance, and this effect is more pronounced in the fast solar wind streams during the solar maximum. We suggest that Coulomb collisions are the main agent leading to merging of the proton beam and core. We are also showing that the variations of the proton beam abundance are correlated with a decrease of the alpha particle velocity in order to maintain the total momentum balance in the solar wind frame.

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Plasma and Magnetic Field Turbulence in the Earth’s Magnetosheath at Ion Scales

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2020.616635 ◽

2021 ◽

Vol 7 ◽

Author(s):

Liudmila Rakhmanova ◽

Maria Riazantseva ◽

Georgy Zastenker

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Solar Wind Plasma ◽

Bow Shock ◽

Present Review ◽

Wind Effects ◽

Earth’S Bow Shock ◽

Magnetic Field Turbulence ◽

Plasma Measurements ◽

Turbulent Cascade

Crossing the Earth’s bow shock is known to crucially affect solar wind plasma including changes in turbulent cascade. The present review summarizes results of more than 15 years of experimental exploration into magnetosheath turbulence. Great contributions to understanding turbulence development inside the magnetosheath was made by means of recent multi-spacecraft missions. We introduce the main results provided by them together with first observations of the turbulent cascade based on direct plasma measurements by the Spektr-R spacecraft in the magnetosheath. Recent results on solar wind effects on turbulence in the magnetosheath are also discussed.

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Coulomb collisions in the solar wind

Journal of Geophysical Research Atmospheres ◽

10.1029/ja090ia08p07389 ◽

1985 ◽

Vol 90 (A8) ◽

pp. 7389-7395 ◽

Cited By ~ 13

Author(s):

L. W. Klein ◽

K. W. Ogilvie ◽

L. F. Burlaga

Keyword(s):

Solar Wind ◽

Coulomb Collisions

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Influence of Coulomb collisions on isotopic and elemental fractionation in the solar wind acceleration process

Journal of Geophysical Research Atmospheres ◽

10.1029/1999ja900434 ◽

2000 ◽

Vol 105 (A1) ◽

pp. 47-60 ◽

Cited By ~ 50

Author(s):

Roland Bodmer ◽

Peter Bochsler

Keyword(s):

Solar Wind ◽

Acceleration Process ◽

Coulomb Collisions ◽

Elemental Fractionation ◽

Solar Wind Acceleration

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The formation and evolution of the electron strahl in the inner heliosphere

10.5194/egusphere-egu21-5152 ◽

2021 ◽

Author(s):

Seong-Yeop Jeong ◽

Daniel Verscharen ◽

Vocks Christian ◽

Christopher Owen ◽

Robert Wicks ◽

...

Keyword(s):

Solar Wind ◽

Velocity Distribution Function ◽

Electron Velocity ◽

Electron Velocity Distribution ◽

Electron Velocity Distribution Function ◽

Coulomb Collisions ◽

Spiral Geometry ◽

Formation And Evolution ◽

Radial Evolution ◽

Inner Heliosphere

The electrons in the solar wind exhibit an interesting kinetic substructure with many important implications for the overall energetics of the plasma in the heliosphere. We are especially interested in the formation and evolution of the electron strahl, a field-aligned beam of superthermal electrons, in the heliosphere. We develop a kinetic transport equation for typical heliospheric conditions based on a Parker-spiral geometry of the magnetic field. We present the results of our theoretical model for the radial evolution of the electron velocity distribution function (VDF) in the solar wind. We study the effects of the adiabatic focusing of energetic electrons, wave-particle interactions, and Coulomb collisions through a generalized kinetic equation for the electron VDF. We compare and contrast our results with the observed effects in the electron VDFs from space missions that explore the radial evolution of electrons in the inner heliosphere such as Helios, Parker Solar Probe, and Solar Orbiter.

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