Model of imbalanced kinetic Alfvén turbulence with energy exchange between dominant and subdominant components

2020 ◽  
Vol 497 (3) ◽  
pp. 3472-3476 ◽  
Author(s):  
G Gogoberidze ◽  
Y M Voitenko
Keyword(s):  
Solar Wind ◽  
Energy Exchange ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
The Sun ◽  
Fast Solar Wind ◽  
Dominant Component ◽  
Propagating Waves ◽  
Non Linear ◽  
Linear Interactions

ABSTRACT Alfvénic turbulence in the fast solar wind is imbalanced: the energy of the (dominant) waves propagating outward from the Sun is much larger than energy of inward-propagating (subdominant) waves. At large scales Alfvén waves are non-dispersive and turbulence is driven by non-linear interactions of counter-propagating waves. Contrary to this, at kinetic scales Alfvén waves become dispersive and non-linear interactions become possible among co-propagating waves as well. The study of the transition between these two regimes of Alfvénic turbulence is important for understanding of complicated dynamics of imbalanced Alfvénic turbulence. In this paper, we present a semiphenomenological model of the imbalanced Alfvénic turbulence accounting for the energy exchange between the dominant and subdominant wave fractions. The energy transfer becomes non-negligible at sufficiently small yet still larger than the ion gyroradius scales and is driven by the non-linear beatings between dispersive dominant(subdominant) waves pumping energy into the subdominant(dominant) component. Our results demonstrate that the turbulence imbalance should decrease significantly in the weakly dispersive wavenumber range.

scholarly journals Solar wind and kinetic heliophysics

2018 ◽  
Vol 36 (6) ◽  
pp. 1607-1630 ◽  
Author(s):  
Eckart Marsch
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Heavy Ion ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Slow Solar Wind ◽  
Alfvén Waves ◽  
The Sun ◽  
Collisionless Dissipation

Abstract. This paper reviews recent aspects of solar wind physics and elucidates the role Alfvén waves play in solar wind acceleration and turbulence, which prevail in the low corona and inner heliosphere. Our understanding of the solar wind has made considerable progress based on remote sensing, in situ measurements, kinetic simulation and fluid modeling. Further insights are expected from such missions as the Parker Solar Probe and Solar Orbiter. The sources of the solar wind have been identified in the chromospheric network, transition region and corona of the Sun. Alfvén waves excited by reconnection in the network contribute to the driving of turbulence and plasma flows in funnels and coronal holes. The dynamic solar magnetic field causes solar wind variations over the solar cycle. Fast and slow solar wind streams, as well as transient coronal mass ejections, are generated by the Sun's magnetic activity. Magnetohydrodynamic turbulence originates at the Sun and evolves into interplanetary space. The major Alfvén waves and minor magnetosonic waves, with an admixture of pressure-balanced structures at various scales, constitute heliophysical turbulence. Its spectra evolve radially and develop anisotropies. Numerical simulations of turbulence spectra have reproduced key observational features. Collisionless dissipation of fluctuations remains a subject of intense research. Detailed measurements of particle velocity distributions have revealed non-Maxwellian electrons, strongly anisotropic protons and heavy ion beams. Besides macroscopic forces in the heliosphere, local wave–particle interactions shape the distribution functions. They can be described by the Boltzmann–Vlasov equation including collisions and waves. Kinetic simulations permit us to better understand the combined evolution of particles and waves in the heliosphere.

scholarly journals Solar Wind and Kinetic Heliophysics

2018 ◽  
Author(s):  
Eckart Marsch
Keyword(s):  
Solar Wind ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Heavy Ion ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Slow Solar Wind ◽  
Alfvén Waves ◽  
The Sun ◽  
Collisionless Dissipation

Abstract. This lecture reviews recent aspects of solar wind physics and elucidates the role Alfvén waves play in solar wind acceleration and turbulence, which prevail in the low corona and inner heliosphere. Our understanding of the solar wind has made considerable progress based on remote sensing, in-situ measurements, kinetic simulation and fluid modeling. Further insights are expected from such missions as the Parker Solar Probe and Solar Orbiter. The sources of the solar wind have been identified in the chromospheric network, Transition region and corona of the sun. Alfvén waves excited by reconnection in the network contribute to the driving of turbulence and plasma flows in funnels and coronal holes. The dynamic solar magnetic field causes solar wind variations over the solar cycle. Fast and slow solar wind streams, as well as transient coronal mass ejections are generated by the sun’s magnetic activity. Magnetohydrodynamic turbulence originates at the sun and evolves into interplanetary space. The major Alfvén waves and minor magnetosonic waves, with an admixture of pressurebalanced structures at various scales, constitute heliophysical turbulence. Its spectra evolve radially and develop anisotropies. Numerical simulations of turbulence spectra have reproduced key observational features. Collisionless dissipation of fluctuations remains a subject of intense research. Detailed measurements of particle velocity distributions have revealed non-maxwellian electrons, strongly anisotropic protons and heavy ion beams. Besides macroscopic forces in the heliosphere local wave-particle interactions shape the distribution functions. They can be described by the Boltzmann–Vlasov equation including collisions and waves. Kinetic simulations permit us to better understand the combined evolution of particles and waves in the heliosphere.

scholarly journals Parametric instability, inverse cascade and the  range of solar-wind turbulence

2018 ◽  
Vol 84 (1) ◽  
Author(s):  
Benjamin D. G. Chandran
Keyword(s):  
Solar Wind ◽  
Nonlinear Evolution ◽  
Parametric Instability ◽  
Alfven Waves ◽  
Turbulence Theory ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Fast Solar Wind ◽  
Parametric Decay ◽  
Inverse Cascade

In this paper, weak-turbulence theory is used to investigate the nonlinear evolution of the parametric instability in three-dimensional low-$\unicode[STIX]{x1D6FD}$ plasmas at wavelengths much greater than the ion inertial length under the assumption that slow magnetosonic waves are strongly damped. It is shown analytically that the parametric instability leads to an inverse cascade of Alfvén wave quanta, and several exact solutions to the wave kinetic equations are presented. The main results of the paper concern the parametric decay of Alfvén waves that initially satisfy $e^{+}\gg e^{-}$, where $e^{+}$ and $e^{-}$ are the frequency ($f$) spectra of Alfvén waves propagating in opposite directions along the magnetic field lines. If $e^{+}$ initially has a peak frequency $f_{0}$ (at which $fe^{+}$ is maximized) and an ‘infrared’ scaling $f^{p}$ at smaller $f$ with $-1<p<1$, then $e^{+}$ acquires an $f^{-1}$ scaling throughout a range of frequencies that spreads out in both directions from $f_{0}$. At the same time, $e^{-}$ acquires an $f^{-2}$ scaling within this same frequency range. If the plasma parameters and infrared $e^{+}$ spectrum are chosen to match conditions in the fast solar wind at a heliocentric distance of 0.3 astronomical units (AU), then the nonlinear evolution of the parametric instability leads to an $e^{+}$ spectrum that matches fast-wind measurements from the Helios spacecraft at 0.3 AU, including the observed $f^{-1}$ scaling at $f\gtrsim 3\times 10^{-4}~\text{Hz}$. The results of this paper suggest that the $f^{-1}$ spectrum seen by Helios in the fast solar wind at $f\gtrsim 3\times 10^{-4}~\text{Hz}$ is produced in situ by parametric decay and that the $f^{-1}$ range of $e^{+}$ extends over an increasingly narrow range of frequencies as $r$ decreases below 0.3 AU. This prediction will be tested by measurements from the Parker Solar Probe.

scholarly journals On the cascade processes of Alfvén waves in the fast solar wind

1999 ◽  
Vol 104 (A11) ◽  
pp. 24819-24834 ◽  
Author(s):  
You Qiu Hu ◽  
Shadia Rifai Habbal ◽  
Xing Li
Keyword(s):  
Solar Wind ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Fast Solar Wind ◽  
Cascade Processes
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