Variability of the Magnetic Field Power Spectrum in the Solar Wind at Electron Scales

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http://hdl.handle.net/10138/229256

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Roberts , O W , Alexandrova , O , Kajdic , P , Turc , L , Perrone , D , Escoubet , C P & Walsh , A 2017 , ' Variability of the Magnetic Field Power Spectrum in the Solar Wind at Electron Scales ' , Astrophysical Journal , vol. 850 , no. 2 , 120 . https://doi.org/10.3847/1538-4357/aa93e5

Title: Variability of the Magnetic Field Power Spectrum in the Solar Wind at Electron Scales
Author: Roberts, Owen Wyn; Alexandrova, O.; Kajdic, P.; Turc, L.; Perrone, D.; Escoubet, C. P.; Walsh, A.
Other contributor: University of Helsinki, Department of Physics

Date: 2017-12-01
Language: eng
Number of pages: 13
Belongs to series: Astrophysical Journal
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/aa93e5
URI: http://hdl.handle.net/10138/229256
Abstract: At electron scales, the power spectrum of solar-wind magnetic fluctuations can be highly variable and the dissipation mechanisms of the magnetic energy into the various particle species is under debate. In this paper, we investigate data from the Cluster mission's STAFF Search Coil magnetometer when the level of turbulence is sufficiently high that the morphology of the power spectrum at electron scales can be investigated. The Cluster spacecraft sample a disturbed interval of plasma where two streams of solar wind interact. Meanwhile, several discontinuities (coherent structures) are seen in the large-scale magnetic field, while at small scales several intermittent bursts of wave activity (whistler waves) are present. Several different morphologies of the power spectrum can be identified: (1) two power laws separated by a break, (2) an exponential cutoff near the Taylor shifted electron scales, and (3) strong spectral knees at the Taylor shifted electron scales. These different morphologies are investigated by using wavelet coherence, showing that, in this interval, a clear break and strong spectral knees are features that are associated with sporadic quasi parallel propagating whistler waves, even for short times. On the other hand, when no signatures of whistler waves at similar to 0.1-0.2f(ce) are present, a clear break is difficult to find and the spectrum is often more characteristic of a power law with an exponential cutoff.
Subject: solar wind
turbulence
waves
ASTROPHYSICAL GYROKINETICS
DISSIPATION RANGE
WAVELET ANALYSIS
CLUSTER MISSION
PHASE COHERENCE
MHD WAVES
1 AU
TURBULENCE
FLUCTUATIONS
MAGNETOSHEATH
115 Astronomy, Space science
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