Temperature anisotropy and differential streaming of solar wind ions -- Correlations with transverse fluctuations

Abstract

We study correlations of the temperature ratio (which is an indicator for perpendicular ion heating) and the differential flow of the alpha particles with the power of transverse fluctuations that have wave numbers between 0.01 and 0.1 (normalized to $k_p=1/l_p$, where $l_p$ is the proton inertial length). We found that both the normalized differential ion speed, $V_{\alpha p}/V_{\mathrm{A}}$ (where $V_{\mathrm{A}}$ is the Alfvén speed) and the proton temperature anisotropy, $T_{\perp p}/T_{\parallel p}$, increase when the relative wave power is growing. Furthermore, if the normalized differential ion speed stays below 0.5, the alpha-particle temperature anisotropy, $T_{\perp \alpha }/T_{\parallel \alpha }$, correlates positively with the relative power of the transverse fluctuations. However, if $V_{\alpha p}/V_{\mathrm{A}}$ is higher than 0.6, then the alpha-particle temperature anisotropy tends to become lower and attain even values below unity despite the presence of transverse fluctuations of relatively high amplitudes. Our findings appear to be consistent with the expectations from kinetic theory for the resonant interaction of the ions with Alfvén/ion-cyclotron waves and the resulting wave dissipation.

5 pages, 4 figures, accepted for publication in Astronomy and Astrophysics journal

References in corpus (3)

• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Alfven Wave Turbulence and Perpendicular Ion Temperatures in Coronal Holes
• Correlations between the proton temperature anisotropy and transverse high-frequency waves in the solar wind

Cited by in corpus (10)

• Solar Wind Turbulence and the Role of Ion Instabilities
• Vlasov simulations of multi-ion plasma turbulence in the solar wind
• Ensemble Simulations of Proton Heating in the Solar Wind via Turbulence and Ion Cyclotron Resonance
• Limits on Alpha Particle Temperature Anisotropy and Differential Flow from Kinetic Instabilities: Solar Wind Observations
• Self-Consistent Ion Cyclotron Anisotropy-Beta Relation for Solar Wind Protons
• Nonlinear Evolution of Ion Kinetic Instabilities in the Solar Wind
• Minor ion heating in spectra of linearly and circularly polarized Alfvén waves: Thermal and non-thermal motions associated with perpendicular heating
• Towards a realistic evaluation of transport coefficients in non-equilibrium space plasmas
• Compound Effect of Alfvén Waves and Ion-cyclotron Waves on Heating/Acceleration of Minor Ions via the Pickup Process
• Transport coefficients enhanced by suprathermal particles in nonequilibrium heliospheric plasmas