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Title: The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence

Abstract

In order to resolve and characterize anisotropy in turbulent plasma flows, a proper estimation of the background magnetic field is crucially important. Various approaches to calculating the background magnetic field, ranging from local to globally averaged fields, are commonly used in the analysis of turbulent data. We investigate how the uncertainty in the orientation of a scale-dependent background magnetic field influences the ability to resolve anisotropy. Therefore, we introduce a quantitative measure, the angle uncertainty, that characterizes the uncertainty of the orientation of the background magnetic field that turbulent structures are exposed to. The angle uncertainty can be used as a condition to estimate the ability to resolve anisotropy with certain accuracy. We apply our description to resolve the spectral anisotropy in fast solar wind data. We show that, if the angle uncertainty grows too large, the power of the turbulent fluctuations is attributed to false local magnetic field angles, which may lead to an incorrect estimation of the spectral indices. In our results, an apparent robustness of the spectral anisotropy to false local magnetic field angles is observed, which can be explained by a stronger increase of power for lower frequencies when the scale of the local magnetic fieldmore » is increased. The frequency-dependent angle uncertainty is a measure that can be applied to any turbulent system.« less

Authors:
; ;  [1]
  1. Institute of Geophysics and Meteorology, University of Cologne, Cologne (Germany)
Publication Date:
OSTI Identifier:
22663460
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 843; 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; ACCURACY; ANISOTROPY; FLUCTUATIONS; FREQUENCY DEPENDENCE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; SOLAR WIND; TURBULENCE

Citation Formats

Gerick, F., Saur, J., and Papen, M. von, E-mail: felix.gerick@uni-koeln.de. The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA767C.
Gerick, F., Saur, J., & Papen, M. von, E-mail: felix.gerick@uni-koeln.de. The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence. United States. doi:10.3847/1538-4357/AA767C.
Gerick, F., Saur, J., and Papen, M. von, E-mail: felix.gerick@uni-koeln.de. Sat . "The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence". United States. doi:10.3847/1538-4357/AA767C.
@article{osti_22663460,
title = {The Uncertainty of Local Background Magnetic Field Orientation in Anisotropic Plasma Turbulence},
author = {Gerick, F. and Saur, J. and Papen, M. von, E-mail: felix.gerick@uni-koeln.de},
abstractNote = {In order to resolve and characterize anisotropy in turbulent plasma flows, a proper estimation of the background magnetic field is crucially important. Various approaches to calculating the background magnetic field, ranging from local to globally averaged fields, are commonly used in the analysis of turbulent data. We investigate how the uncertainty in the orientation of a scale-dependent background magnetic field influences the ability to resolve anisotropy. Therefore, we introduce a quantitative measure, the angle uncertainty, that characterizes the uncertainty of the orientation of the background magnetic field that turbulent structures are exposed to. The angle uncertainty can be used as a condition to estimate the ability to resolve anisotropy with certain accuracy. We apply our description to resolve the spectral anisotropy in fast solar wind data. We show that, if the angle uncertainty grows too large, the power of the turbulent fluctuations is attributed to false local magnetic field angles, which may lead to an incorrect estimation of the spectral indices. In our results, an apparent robustness of the spectral anisotropy to false local magnetic field angles is observed, which can be explained by a stronger increase of power for lower frequencies when the scale of the local magnetic field is increased. The frequency-dependent angle uncertainty is a measure that can be applied to any turbulent system.},
doi = {10.3847/1538-4357/AA767C},
journal = {Astrophysical Journal},
number = 1,
volume = 843,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}