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Title: ON ELECTRON-SCALE WHISTLER TURBULENCE IN THE SOLAR WIND

Abstract

For the first time, the dispersion relation for turbulence magnetic field fluctuations in the solar wind is determined directly on small scales of the order of the electron inertial length, using four-point magnetometer observations from the Magnetospheric Multiscale mission. The data are analyzed using the high-resolution adaptive wave telescope technique. Small-scale solar wind turbulence is primarily composed of highly obliquely propagating waves, with dispersion consistent with that of the whistler mode.

Authors:
; ; ; ;  [1];  [2];  [3];  [4];  [5]; ;  [6];  [7];  [8];  [9];  [10]
  1. Space Research Institute, Austrian Academy of Sciences, Graz (Austria)
  2. Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig (Germany)
  3. Institut für Theoretische Physik, Technische Universität Braunschweig, Braunschweig (Germany)
  4. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
  5. University of New Hampshire, Durham, NH (United States)
  6. University of California Los Angeles, Los Angeles, CA (United States)
  7. Southwest Research Institute, San Antonio, TX (United States)
  8. University of Toyama, Faculty of Human Development, Toyama (Japan)
  9. Graduate School of Science, Nagoya University, Institute for Space-Earth Environmental Research, Nagoya (Japan)
  10. Space Science Institute, Los Alamos, NM (United States)
Publication Date:
OSTI Identifier:
22654250
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 827; 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; DISPERSION RELATIONS; DISPERSIONS; ELECTRONS; FLUCTUATIONS; MAGNETIC FIELDS; MAGNETOMETERS; PLASMA; RESOLUTION; SOLAR WIND; TELESCOPES; TURBULENCE; WHISTLER INSTABILITY; WHISTLERS

Citation Formats

Narita, Y., Nakamura, R., Baumjohann, W., Magnes, W., Fischer, D., Glassmeier, K.-H., Motschmann, U., Giles, B., Torbert, R. B., Russell, C. T., Strangeway, R. J., Burch, J. L., Nariyuki, Y., Saito, S., and Gary, S. P., E-mail: yasuhito.narita@oeaw.ac.at. ON ELECTRON-SCALE WHISTLER TURBULENCE IN THE SOLAR WIND. United States: N. p., 2016. Web. doi:10.3847/2041-8205/827/1/L8.
Narita, Y., Nakamura, R., Baumjohann, W., Magnes, W., Fischer, D., Glassmeier, K.-H., Motschmann, U., Giles, B., Torbert, R. B., Russell, C. T., Strangeway, R. J., Burch, J. L., Nariyuki, Y., Saito, S., & Gary, S. P., E-mail: yasuhito.narita@oeaw.ac.at. ON ELECTRON-SCALE WHISTLER TURBULENCE IN THE SOLAR WIND. United States. doi:10.3847/2041-8205/827/1/L8.
Narita, Y., Nakamura, R., Baumjohann, W., Magnes, W., Fischer, D., Glassmeier, K.-H., Motschmann, U., Giles, B., Torbert, R. B., Russell, C. T., Strangeway, R. J., Burch, J. L., Nariyuki, Y., Saito, S., and Gary, S. P., E-mail: yasuhito.narita@oeaw.ac.at. Wed . "ON ELECTRON-SCALE WHISTLER TURBULENCE IN THE SOLAR WIND". United States. doi:10.3847/2041-8205/827/1/L8.
@article{osti_22654250,
title = {ON ELECTRON-SCALE WHISTLER TURBULENCE IN THE SOLAR WIND},
author = {Narita, Y. and Nakamura, R. and Baumjohann, W. and Magnes, W. and Fischer, D. and Glassmeier, K.-H. and Motschmann, U. and Giles, B. and Torbert, R. B. and Russell, C. T. and Strangeway, R. J. and Burch, J. L. and Nariyuki, Y. and Saito, S. and Gary, S. P., E-mail: yasuhito.narita@oeaw.ac.at},
abstractNote = {For the first time, the dispersion relation for turbulence magnetic field fluctuations in the solar wind is determined directly on small scales of the order of the electron inertial length, using four-point magnetometer observations from the Magnetospheric Multiscale mission. The data are analyzed using the high-resolution adaptive wave telescope technique. Small-scale solar wind turbulence is primarily composed of highly obliquely propagating waves, with dispersion consistent with that of the whistler mode.},
doi = {10.3847/2041-8205/827/1/L8},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 827,
place = {United States},
year = {Wed Aug 10 00:00:00 EDT 2016},
month = {Wed Aug 10 00:00:00 EDT 2016}
}
  • Turbulence at MagnetoHydroDynamics (MHD) scales of the solar wind has been studied for more than three decades, using data analyzes, theoretical and numerical modeling. However smaller scales have not been explored until very recently. Here, we review recent results on the first observation of cascade and dissipation of the solar wind turbulence at the electron scales. Thanks to the high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectra of turbulence up to {approx}100 Hz (in the spacecraft reference frame) and found two distinct breakpoints in the magnetic spectrum at 0.4 Hz and 35 Hz,more » which correspond, respectively, to the Doppler-shifted proton and electron gyroscales, f{sub {rho}p} and f{sub {rho}e}. Below f{sub {rho}p} the spectrum follows a Kolmogorov scaling f{sup -1.62}, typical of spectra observed at 1 AU. Above f{sub {rho}p} a second inertial range is formed with a scaling f{sup -2.3} down to f{sub {rho}e}. Above f{sub {rho}e} the spectrum has a steeper power law {approx}f{sup -4.1} down to the noise level of the instrument. Solving numerically the linear Maxwell-Vlasov equations combined with recent theoretical predictions of the Gyro-Kinetic theory, we show that the present results are fully consistent with a scenario of a quasi-two-dimensional cascade into Kinetic Alfven modes (KAW).« less
  • We summarize our recent studies on the origin of solar wind kinetic scale turbulence and electron halo in the electron velocity distribution function. Increasing observations of nanoflares and microscopic type III radio bursts strongly suggest that nanoflares and accelerated electron beams are common in the corona. Based on particle-in-cell simulations, we show that both the core-halo feature and kinetic scale turbulence observed in the solar wind can be produced by the nonlinear evolution of electron two-stream instability driven by nanoflare accelerated electron beams. The energy exchange between waves and particles reaches equilibrium in the inner corona and the key featuresmore » of the turbulence and velocity distribution are preserved as the solar wind escapes into interplanetary space along open magnetic field lines. Observational tests of the model and future theoretical work are discussed.« less
  • Magnetic field fluctuations with frequencies f between the ion ( f/sub c/i) and electron ( f/sub c/e) cyclotron frequencies are enhanced downstream of interplanetary shocks and in fast streams. These f>f/sub c/i fluctuations are related to those below f/sub c/i that also accompany solar wind activity. The spectra over the range 10/sup -2/ f/sub c/i < or =f< or approx. = f/sub c/e synthesized from ISEE3 magnetometer and plasma wave instrument data can generally be described by one power law below froughly-equal1 Hzroughly-equalf/sub c/i and a different one above. However, behind four shocks the spectral index above f/sub c/i wasmore » measured to be about twice that below f/sub c/i, whereas no clear relationship is apparent in the weaker fast stream events. Behind one shock the interference in the low-frequency electric field channels of the ISEE3 plasma wave instrument was small enough to permit a statistical study of the B/E ratios or, equivalently, the indices of refraction, of the f/sub c/i < or =f< or =f/sub c/e waves. Although the data base is limited, the B/E ratios confirm that the waves are whistler mode emissions, as their frequency range already suggested. Various indirect lines of evidence indicate that these whistler waves are generated propagating at large angles to the local interplanetary field, a fact that helps identify possible free energy sources for their growth.« less
  • To determine the wave modes prevailing in solar wind turbulence at kinetic scales, we study the magnetic polarization of small-scale fluctuations in the plane perpendicular to the data sampling direction (namely, the solar wind flow direction, V{sub SW}) and analyze its orientation with respect to the local background magnetic field B{sub 0,local}. As an example, we take only measurements made in an outward magnetic sector. When B{sub 0,local} is quasi-perpendicular to V{sub SW}, we find that the small-scale magnetic-field fluctuations, which have periods from about 1 to 3 s and are extracted from a wavelet decomposition of the original timemore » series, show a polarization ellipse with right-handed orientation. This is consistent with a positive reduced magnetic helicity, as previously reported. Moreover, for the first time we find that the major axis of the ellipse is perpendicular to B{sub 0,local}, a property that is characteristic of an oblique Alfven wave rather than oblique whistler wave. For an oblique whistler wave, the major axis of the magnetic ellipse is expected to be aligned with B{sub 0,local}, thus indicating significant magnetic compressibility, and the polarization turns from right to left handedness as the wave propagation angle ({theta}{sub kB}) increases toward 90 Degree-Sign . Therefore, we conclude that the observation of a right-handed polarization ellipse with orientation perpendicular to B{sub 0,local} seems to indicate that oblique Alfven/ion-cyclotron waves rather than oblique fast-mode/whistler waves dominate in the 'dissipation' range near the break of solar wind turbulence spectra occurring around the proton inertial length.« less
  • It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore, in the high-beta solar wind plasma, whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently, the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers can survive because the background kinetic Alfven wave (KAW) turbulence creates a plateau by quasilinear (QL) diffusion in the solar wind electron distribution atmore » small velocities. It is found that for whistler energy density of only {approx}10{sup -3} that of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers is comparable to KAW. Thus, very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function.« less