scholarly journals Correlations between the proton temperature anisotropy and transverse high-frequency waves in the solar wind

2010 ◽  
Vol 37 (14) ◽  
pp. n/a-n/a ◽  
Author(s):  
Sofiane Bourouaine ◽  
Eckart Marsch ◽  
Fritz M. Neubauer
Keyword(s):  
Solar Wind ◽  
High Frequency ◽  
Temperature Anisotropy ◽  
Proton Temperature ◽  
High Frequency Waves

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 Properties of A Supercritical Quasi-Perpendicular Interplanetary Shock Propagating in Super-Alfvénic Solar Wind: from MHD to Kinetic Scales

2021 ◽  
Author(s):  
Mingzhe Liu ◽  
Zhongwei Yang ◽  
Ying D. Liu ◽  
Bertrand Lembege ◽  
Karine Issautier ◽  
...  
Keyword(s):  
Solar Wind ◽  
Energy Dissipation ◽  
Interplanetary Shock ◽  
Particle Interactions ◽  
Temperature Anisotropy ◽  
Ion Cyclotron Waves ◽  
Proton Temperature ◽  
Ion Cyclotron ◽  
Mirror Mode

<p>We investigate the properties of an interplanetary shock (M<sub>A</sub>=3.0, θ<sub>Bn</sub>=80°) propagating in Super-Alfvénic solar wind observed on September 12<sup>th,</sup> 1999 with in situ Wind/MFI and Wind/3DP observations. Key results are obtained concerning the possible energy dissipation mechanisms across the shock and how the shock modifies the ambient solar wind at MHD and kinetic scales:  (1) Waves observed in the far upstream of the shock are incompressional and mostly shear Alfvén waves.  (2) In the downstream, the shocked solar wind shows both Alfvénic and mirror-mode features due to the coupling between the Alfvén waves and ion mirror-mode waves.  (3) Specularly reflected gyrating ions, whistler waves, and ion cyclotron waves are observed around the shock ramp, indicating that the shock may rely on both particle reflection and wave-particle interactions for energy dissipation.  (4) Both ion cyclotron and mirror mode instabilities may be excited in the downstream of the shock since the proton temperature anisotropy touches their thresholds due to the enhanced proton temperature anisotropy.  (5) Whistler heat flux instabilities excited around the shock give free energy for the whistler precursors, which help explain the isotropic electron number and energy flux together with the normal betatron acceleration of electrons across the shock.  (6) The shock may be somehow connected to the electron foreshock region of the Earth’s bow shock, since Bx > 0, By < 0, and the electron flux varies only when the electron pitch angles are less than PA = 90°, which should be further investigated. Furthermore, the interaction between Alfvén waves and the shock and how the shock modifies the properties of the Alfvén waves are also discussed.</p>

scholarly journals Combined electron firehose and electromagnetic ion cyclotron instabilities: quasilinear approach

2020 ◽  
Vol 499 (1) ◽  
pp. 659-667
Author(s):  
Z Ali ◽  
M Sarfraz ◽  
P H Yoon
Keyword(s):  
Solar Wind ◽  
Dynamical Evolution ◽  
Solar Wind Plasma ◽  
Distribution Functions ◽  
Temperature Anisotropy ◽  
Spatial And Temporal Scales ◽  
Proton Temperature ◽  
Ion Cyclotron ◽  
Velocity Distribution Functions ◽  
High Beta

ABSTRACT Various plasma waves and instabilities are abundantly present in the solar wind plasma, as evidenced by spacecraft observations. Among these, propagating modes and instabilities driven by temperature anisotropies are known to play a significant role in the solar wind dynamics. In situ measurements reveal that the threshold conditions for these instabilities adequately explain the solar wind conditions at large heliocentric distances. This paper pays attention to the combined effects of electron firehose instability driven by excessive parallel electron temperature anisotropy (T⊥e < T∥e) at high beta conditions, and electromagnetic ion cyclotron instability driven by excessive perpendicular proton temperature anisotropy (T⊥i > T∥i). By employing quasilinear kinetic theory based upon the assumption of bi-Maxwellian velocity distribution functions for protons and electrons, the dynamical evolution of the combined instabilities and their mutual interactions mediated by the particles is explored in depth. It is found that while in some cases, the two unstable modes are excited and saturated at distinct spatial and temporal scales, in other cases, the two unstable modes are intermingled such that a straightforward interpretation is not so easy. This shows that when the dynamics of protons and electrons are mutually coupled and when multiple unstable modes are excited in the system, the dynamical consequences can be quite complex.

Proton temperature anisotropy instabilities in the solar wind

1976 ◽  
Vol 81 (7) ◽  
pp. 1241-1246 ◽  
Author(s):  
S. Peter Gary ◽  
M. D. Montgomery ◽  
W. C. Feldman ◽  
D. W. Forslund
Keyword(s):  
Solar Wind ◽  
Temperature Anisotropy ◽  
Proton Temperature

On the Solar Wind Proton Temperature Anisotropy at Mars' Orbital Location

2021 ◽  
Vol 126 (10) ◽  
Author(s):  
C. L. Lentz ◽  
A. Chasapis ◽  
R. A. Qudsi ◽  
J. Halekas ◽  
B. A. Maruca ◽  
...  
Keyword(s):  
Solar Wind ◽  
Temperature Anisotropy ◽  
Solar Wind Proton ◽  
Proton Temperature

Solar wind temperature anisotropy and its influence on the spectrum of turbulence

2020 ◽  
Author(s):  
Alexander Pitňa ◽  
Jana Šafránkova ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Power Spectra ◽  
Solar Wind Plasma ◽  
Turbulent Medium ◽  
Thermal Velocity ◽  
Temperature Anisotropy ◽  
Ion Density ◽  
Proton Temperature ◽  
Wind Spacecraft

<p>Nearly collisionless solar wind plasma originating in the solar corona is a turbulent medium. The energy within large scale fluctuations is continuously transferred into smaller scales and it eventually reaches scales at which it is converted into a random particle motion, thus heating the plasma. Although the processes that take place within this complex system have been studied for decades, many questions remain unresolved. The power spectra of the fluctuating fields of the magnetic field, bulk velocity, and ion density were studied extensively; however, the spectrum of the thermal velocity is seldom reported and/or discussed. In this paper, we address the difficulty of estimating its power spectrum. We analyze high-cadence (31 ms) thermal velocity measurements of the BMSW instrument onboard the Spektr-R spacecraft and the SWE instrument onboard the Wind spacecraft. We discuss the role of the proton temperature anisotropy (parallel/perpendicular) and its influence on the shape of the power spectra in the inertial range of turbulence.</p>

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