The Electron Structure of the Solar Wind

Time-series measurements of the number density ncore and temperature Tcore of the core-electron population of the solar wind are examined at 1 AU and at 0.13 AU using measurements from the WIND and Parker Solar Probe spacecraft, respectively. A statistical analysis of the ncore and Tcore measurements at 1 AU finds that the core-electron spatial structure of the solar wind is related to the magnetic-flux-tube structure of the solar wind; this electron structure is characterized by jumps in the values of ncore and Tcore when passing from one magnetic flux tube into the next. The same types of flux-tube jumps are seen for Tcore at 0.13 AU. Some models of the interplanetary electrical potential of the heliosphere predict that Tcore is a direct measure of the local electrical potential in the heliosphere. If so, then jumps seen in Tcore represent jumps in the electrical potential from flux tube to flux tube. This may imply that the interplanetary electrical potential (and its effect on the radial evolution away from the Sun of solar-wind ions and electrons) independently operates in each flux tube of the heliosphere.

Evolution of the MHD turbulence properties in the inner heliosphere with the PSP/SolO alignment data

<p>Radial alignments between pairs of spacecraft is the only way to observationally investigate the turbulent evolution of the solar wind as it expands throughout interplanetary space. On September 2020 Parker Solar Probe (PSP) and Solar Orbiter (SolO) were nearly perfectly radially aligned, with PSP orbiting around its perihelion at 0.1 au (and crossing the nominal Alfvén point) and SolO at 1 au. PSP/SolO joint observations of the same solar wind plasma allow the extraordinary and unprecedented opportunity to study how the turbulence properties of the solar wind evolve in the inner heliosphere over the wide distance of 0.9 au. The radial evolution of (i) the MHD properties (such as radial dependence of low- and high-frequency breaks, compressibility, Alfvénic content of the fluctuations), (ii) the polarization status, (iii) the presence of wave modes at kinetic scale as well as their distribution in the plasma instability-temperature anisotropy plane are just few instances of what can be addressed. Of furthest interest is the study of whether and how the cascade transfer and dissipation rates evolve with the solar distance, since this has great impact on the fundamental plasma physical processes related to the heating of the solar wind. In this talk I will present some of the results obtained by exploiting the PSP/SolO alignment data.</p>

Theory and observations of switchbacks’ evolution in the solar wind

<p>Alfvénic fluctuations represent the dominant contributions to turbulent fluctuations in the solar wind, especially, but not limited to, the fastest streams with velocity of the order of 600-700 km/s. Alfvénic fluctuations can contribute to solar wind heating and acceleration via wave pressure and turbulent heating. Observations show that such fluctuations are characterized by a nearly constant magnetic field amplitude, a condition which remains largely to be understood and that may be an indication of how fluctuations evolve and relax in the expanding solar wind. Interestingly, measurements from Parker Solar Probe have shown the ubiquitous and persistent presence of the so-called switchbacks. These are magnetic field lines which are strongly perturbed to the point that they produce local inversions of the radial magnetic field. The corresponding signature of switchbacks in the velocity field is that of local enhancements in the radial speed (or jets) that display the typical velocity-magnetic field correlation that characterizes Alfvén waves propagating away from the Sun. While there is not yet a general consensus on what is the origin of switchbacks and their connection to coronal activity, a first necessary step to answer these important questions is to understand how they evolve and how long they can persist in the solar wind. Here we investigate the evolution of switchbacks. We address how their evolution is affected by parametric instabilities and the possible role of expansion, by comparing models with the observed radial evolution of the fluctuations’ amplitude. We finally discuss what are the implications of our results for models of switchback generation and related open questions.</p>

Radial Evolution of the Solar Wind and Associating Turbulence Based on the Synergetic Measurement from Parker Solar Probe and 1 au Observations

<div> <div>The 4th encounter (~30 Rs away from the sun) of the Parker Solar Probe (PSP) is a great opportunity to observe the radial evolution of the solar wind from the inner heliosphere to the near-earth environment when the sun, PSP, and the earth are quasi-radial aligned. Similar features of the solar wind are observed from both PSP and Wind (at 1 au) measurements. The accelerating-solar-wind model could be more suitable than the constant speed model for the observation, which means the solar wind is still accelerating from 30 Rs to 1 au. Both PSP and Wind measure the co-existence of the Alfvenic and compressive fluctuations in the solar wind. The correlated radial velocity (dVR), proton density (dn) and temperature (dT) fluctuations indicate the nature of the compressive fluctuations are outward-propagating slow waves. However, dn and dB is not correlated from PSP, but correlated from Wind, which indicates the propagating direction of the slow waves is changed. Comparing the radial evolution of the energies of both Alfvenic and compressive fluctuations with the WKB model, we find the observed energy decays slower than the theoretical prediction, which indicates an extra energy injection during the solar wind propagation.</div> 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--></p>

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

<p>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.</p>

Zonal Detached Eddy Simulation of the Fan-OGV Stage of a Modern Turbofan Engine

The present article deals with the Zonal Detached Eddy Simulation of the fan module of a modern turbofan engine. The fan module, tested at the AneCom facility, is equipped with rotating fan blades and stationary outlet guide vanes (OGV). The simulation was performed to capture the interaction of the turbulent fan wakes with the OGV walls. The final goal of this simulation is the prediction of the associated broadband noise, not adressed here. In this paper, only the aerodynamic aspects are treated. The simulation relies on a hybrid RANS/LES approach with a zonal strategy: the core airflow is treated in RANS while the bypass airflow is solved with the hybrid approach. Mesh criteria meeting both RANS/LES and acoustic requirements were fulfilled, leading to a mesh of 380 million cells. The simulation was performed during five revolutions and statistical convergence was reached. Inspections of the flow-fields highlight a consistent behaviour of the shielding function (border between RANS and LES solving areas) around the blade walls, at the trailing-edge and in the tip gap flow areas. Comparisons with performance and hot-wire measurements are also presented. Aerodynamic performance and radial evolution of averaged velocities on a plane in-between the fan and the OGV are well retrieved, both in shape and levels. For the turbulent quantities, the shape of the radial profiles are close to the measurements, with much better accuracy in the upper region compared to the RANS solution.