Spectral Analysis of Magnetic Fluctuations at Proton Scales from Fast to Slow Solar Wind
Date Issued
2015
Author(s)
Description
This research was partially supported by the Italian Space Agency (ASI) under contracts I/013/12/0 and I/022/10/2, and by the European Commission’s Seventh Framework Program under the grant agreement STORM (project No. 313038). Data from WIND were obtained from NASA-CDAWeb website.
Abstract
This Letter investigates the spectral characteristics of interplanetary magnetic field fluctuations at proton scales during several time intervals chosen along the speed profile of a fast stream. The character of the fluctuations within the first frequency decade, beyond the high-frequency break located between the fluid and kinetic regimes, strongly depends on the type of wind. While the fast wind shows a clear signature of both right-handed and left-handed polarized fluctuations, possibly associated with Kinetic {Alfv}\acute{{{e}}}{{n}} Wave (KAW) and ion-cyclotron waves, respectively, the rarefaction region, where the wind speed and the Alfvénicity of low-frequency fluctuations decrease, shows a rapid disappearance of the ion-cyclotron signature followed by a more gradual disappearance of KAWs. Moreover, the power associated with perpendicular and parallel fluctuations also experiences rapid depletion, however, retaining the power anisotropy in favor of the perpendicular spectrum.
Volume
811
Issue
2
Start page
L17
Issn Identifier
2041-8205
Ads BibCode
2015ApJ...811L..17B
Rights
open.access
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