Alpha/proton instability in the presence of proton and alpha temperature anisotropy and its application to the deceleration of alpha particles in the solar wind

2021 ◽  
Author(s):  
Welu Zhang ◽  
Liang Xiang ◽  
Qiuhuan Li ◽  
Siyi Lang ◽  
Hongwei Yu
Keyword(s):  
Solar Wind ◽  
Alpha Particles ◽  
Temperature Anisotropy

scholarly journals A kinetic model of plasma turbulence

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
S. Servidio ◽  
F. Valentini ◽  
D. Perrone ◽  
A. Greco ◽  
F. Califano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Velocity Distribution Function ◽  
Plasma Turbulence ◽  
Alpha Particles ◽  
Magnetic Field Direction ◽  
Temperature Anisotropy ◽  
Kinetic Effects ◽  
Magnetic Gradients ◽  
Definition Of

A Hybrid Vlasov–Maxwell (HVM) model is presented and recent results about the link between kinetic effects and turbulence are reviewed. Using five-dimensional (2D in space and 3D in the velocity space) simulations of plasma turbulence, it is found that kinetic effects (or non-fluid effects) manifest through the deformation of the proton velocity distribution function (DF), with patterns of non-Maxwellian features being concentrated near regions of strong magnetic gradients. The direction of theproper temperature anisotropy, calculated in the main reference frame of the distribution itself, has a finite probability of being along or across the ambient magnetic field, in general agreement with the classical definition of anisotropyT⊥/T∥(where subscripts refer to the magnetic field direction). Adopting the latter conventional definition, by varying the global plasma beta (β) and fluctuation level, simulations explore distinct regions of the space given byT⊥/T∥and β∥, recovering solar wind observations. Moreover, as in the solar wind, HVM simulations suggest that proton anisotropy is not only associated with magnetic intermittent events, but also with gradient-type structures in the flow and in the density. The role of alpha particles is reviewed using multi-ion kinetic simulations, revealing a similarity between proton and helium non-Maxwellian effects. The techniques presented here are applied to 1D spacecraft-like analysis, establishing a link between non-fluid phenomena and solar wind magnetic discontinuities. Finally, the dimensionality of turbulence is investigated, for the first time, via 6D HVM simulations (3D in both spaces). These preliminary results provide support for several previously reported studies based on 2.5D simulations, confirming several basic conclusions. This connection between kinetic features and turbulence open a new path on the study of processes such as heating, particle acceleration, and temperature-anisotropy, commonly observed in space plasmas.

scholarly journals INSTABILITIES DRIVEN BY THE DRIFT AND TEMPERATURE ANISOTROPY OF ALPHA PARTICLES IN THE SOLAR WIND

2013 ◽  
Vol 773 (2) ◽  
pp. 163 ◽  
Author(s):  
Daniel Verscharen ◽  
Sofiane Bourouaine ◽  
Benjamin D. G. Chandran
Keyword(s):  
Solar Wind ◽  
Alpha Particles ◽  
Temperature Anisotropy

scholarly journals Influence of He++ and shock geometry on interplanetary shocks in the solar wind: 2D Hybrid simulations

2020 ◽  
Author(s):  
Luis Preisser ◽  
Xochitl Blanco-Cano ◽  
Domenico Trotta ◽  
David Burgess ◽  
Primoz Kajdic
Keyword(s):  
Solar Wind ◽  
Velocity Distribution Function ◽  
Interplanetary Shock ◽  
Alpha Particles ◽  
Upstream Region ◽  
Interplanetary Shocks ◽  
Temperature Anisotropy ◽  
Ion Species ◽  
The Magnetic Field ◽  
Hybrid Simulations

<p>Alpha particles (He<sup>++</sup>) are the most important minor ion species in the solar wind, constituting typically about 5% of the total ion number density. When crossing an interplanetary shock protons and He<sup>++</sup> particles are accelerated differently due to their different charge-to-mass ratio. This behavior can produce changes in the velocity distribution function (VDF) for both species in the immediate downstream region generating anisotropy in the temperature which is considered to be the energy source for various phenomena such as ion cyclotron and mirror mode waves for example. How these changes in temperature anisotropy and shock structure depend on the percentage of He<sup>++</sup> particles and the geometry of the shock is not completely understood. In this work we perform various 2D local hybrid simulations (particle ions, massless fluid electrons) with similar characteristics (e.g., Mach number) to observed interplanetary shocks for both quasi-parallel and quasi-perpendicular geometries including self-consistently different percentages of He<sup>++</sup> particles. We find that the change of the initial θ<sub>Bn</sub> leads to variations of the efficiency with which particles can escape to the upstream region facilitating or not the formation of compressive structures in the magnetic field that will produce increments in perpendicular temperature. The regions where both temperature anisotropy and compressive fluctuations appear tend to be more extended and reach higher values as the He<sup>++</sup> content in the simulations increase.</p>

Proton Beam Abundance Variations and Their Relation to Alpha Particle Properties

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.

Analysis of Alfvénic flows with Solar Orbiter: particle and magnetic observations down to kinetic scales.

2021 ◽  
Author(s):  
Philippe Louarn ◽  
Andrei fedorov ◽  
alexis Rouillard ◽  
Benoit Lavraud ◽  
Vincent Génot ◽  
...  
Keyword(s):  
Solar Wind ◽  
Fine Structure ◽  
Time Resolution ◽  
Time Scale ◽  
Residual Energy ◽  
Distribution Functions ◽  
Strongly Correlated ◽  
Temperature Anisotropy ◽  
Velocity Fluctuations ◽  
Turbulence Parameters

<p>The magnetic and velocity fluctuations of the solar wind may be strongly correlated. This characterizes the  ‘Alfvenic’ flows. Using the observations of the Proton Alfa sensor (PAS/SWA) and the magnetometer (MAG) onboard Solar Orbiter, we analyze a period of 100 hours of such alfvenic flows, at different scales. Several parameters of the turbulence are computed (V-B correlation, various spectral indexes, cross-helicity, residual energy). We explore how these parameters may vary with time and characterize different turbulent states of the flow. More specifically, using the unprecedented time resolution of PAS during burst mode, especially its capability to measure 3D distribution functions at time scale below the proton gyroperiod, we study the connection of the turbulence to the dissipation domain and analyze the fine structure of the distribution functions and their evolutions at sub-second scales. The goal is to investigate whether some characteristics of the distributions, as their more or less pronounced temperature anisotropy, may be related to the turbulence parameters and the degree of V-B correlation.</p>

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

2021 ◽  
Author(s):  
Daniele Telloni ◽  
Keyword(s):  
Solar Wind ◽  
High Frequency ◽  
Interplanetary Space ◽  
Solar Wind Plasma ◽  
Radial Dependence ◽  
Physical Processes ◽  
Temperature Anisotropy ◽  
Mhd Turbulence ◽  
Radial Evolution ◽  
Inner Heliosphere

<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>

scholarly journals Geotail observations of temperature anisotropy of the two-component protons in the dusk plasma sheet

2007 ◽  
Vol 25 (3) ◽  
pp. 769-777 ◽  
Author(s):  
M. N. Nishino ◽  
M. Fujimoto ◽  
T. Terasawa ◽  
G. Ueno ◽  
K. Maezawa ◽  
...  
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Transport Process ◽  
Cold Plasma ◽  
Strong Anisotropy ◽  
Temperature Anisotropy ◽  
Low Latitude ◽  
Two Component ◽  
Cold Component

Abstract. In search for clues towards the understanding of the cold plasma sheet formation under northward IMF, we study the temperature anisotropy of the two-component protons in the plasma sheet near the dusk low-latitude boundary observed by the Geotail spacecraft. The two-component protons result from mixing of the cold component from the solar wind and the hot component of the magnetospheric origin, and may be the most eloquent evidence for the transport process across the magnetopause. The cold component occasionally has a strong anisotropy in the dusk flank, and the sense of the anisotropy depends on the observed locations: the parallel temperature is enhanced in the tail flank while the perpendicular temperature is enhanced on the dayside. The hot component is nearly isotropic in the tail while the perpendicular temperature is enhanced on the dayside. We discuss possible mechanism that can lead to the observed temperature anisotropies.

TAUS measurements of non-gyrotropic distribution functions of solar wind alpha particles

1996 ◽  
Author(s):  
H. F. Astudillo ◽  
E. Marsch ◽  
S. Livi ◽  
H. Rosenbauer
Keyword(s):  
Solar Wind ◽  
Distribution Functions ◽  
Alpha Particles
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