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Title: ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE

Abstract

We investigate the properties of plasma fluid motion in the large-amplitude, low-frequency fluctuations of highly Alfvénic fast solar wind. We show that protons locally conserve total kinetic energy when observed from an effective frame of reference comoving with the fluctuations. For typical properties of the fast wind, this frame can be reasonably identified by alpha particles which, due to their drift with respect to protons at about the Alfvén speed along the magnetic field, do not partake in the fluid low-frequency fluctuations. Using their velocity to transform the proton velocity into the frame of Alfvénic turbulence, we demonstrate that the resulting plasma motion is characterized by a constant absolute value of the velocity, zero electric fields, and aligned velocity and magnetic field vectors as expected for unidirectional Alfvénic fluctuations in equilibrium. We propose that this constraint, via the correlation between velocity and magnetic field in Alfvénic turbulence, is the origin of the observed constancy of the magnetic field; while the constant velocity corresponding to constant energy can only be observed in the frame of the fluctuations, the corresponding constant total magnetic field, invariant for Galilean transformations, remains the observational signature in the spacecraft frame of the constant total energy inmore » the Alfvén turbulence frame.« less

Authors:
; ;  [1];  [2];  [3]
  1. The Blackett Laboratory, Imperial College London, SW7 2AZ (United Kingdom)
  2. LESIA, Observatoire de Paris, CNRS, UPMC, Universit Paris-Diderot, 5 Place Jules Janssen, F-92195 Meudon (France)
  3. Department of Earth, Planetary, and Space Sciences, UCLA, California (United States)
Publication Date:
OSTI Identifier:
22522031
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 802; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; ALPHA PARTICLES; ELECTRIC FIELDS; EQUILIBRIUM; FLUCTUATIONS; GALILEI TRANSFORMATIONS; IONS; KINETIC ENERGY; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; SOLAR PROTONS; SOLAR WIND; SPACE VEHICLES; TURBULENCE; VELOCITY

Citation Formats

Matteini, L., Horbury, T. S., Schwartz, S. J., Pantellini, F., and Velli, M.. ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE. United States: N. p., 2015. Web. doi:10.1088/0004-637X/802/1/11.
Matteini, L., Horbury, T. S., Schwartz, S. J., Pantellini, F., & Velli, M.. ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE. United States. doi:10.1088/0004-637X/802/1/11.
Matteini, L., Horbury, T. S., Schwartz, S. J., Pantellini, F., and Velli, M.. Fri . "ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE". United States. doi:10.1088/0004-637X/802/1/11.
@article{osti_22522031,
title = {ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE},
author = {Matteini, L. and Horbury, T. S. and Schwartz, S. J. and Pantellini, F. and Velli, M.},
abstractNote = {We investigate the properties of plasma fluid motion in the large-amplitude, low-frequency fluctuations of highly Alfvénic fast solar wind. We show that protons locally conserve total kinetic energy when observed from an effective frame of reference comoving with the fluctuations. For typical properties of the fast wind, this frame can be reasonably identified by alpha particles which, due to their drift with respect to protons at about the Alfvén speed along the magnetic field, do not partake in the fluid low-frequency fluctuations. Using their velocity to transform the proton velocity into the frame of Alfvénic turbulence, we demonstrate that the resulting plasma motion is characterized by a constant absolute value of the velocity, zero electric fields, and aligned velocity and magnetic field vectors as expected for unidirectional Alfvénic fluctuations in equilibrium. We propose that this constraint, via the correlation between velocity and magnetic field in Alfvénic turbulence, is the origin of the observed constancy of the magnetic field; while the constant velocity corresponding to constant energy can only be observed in the frame of the fluctuations, the corresponding constant total magnetic field, invariant for Galilean transformations, remains the observational signature in the spacecraft frame of the constant total energy in the Alfvén turbulence frame.},
doi = {10.1088/0004-637X/802/1/11},
journal = {Astrophysical Journal},
number = 1,
volume = 802,
place = {United States},
year = {Fri Mar 20 00:00:00 EDT 2015},
month = {Fri Mar 20 00:00:00 EDT 2015}
}