Radial Evolution of Spectral Characteristics of Magnetic Field Fluctuations at Proton Scales
Journal
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 n° 313038). Data from Wind and Messenger were obtained from NASA-CDAWeb and NASA-PDS websites, respectively.
Abstract
This paper addresses the investigation of the character and the radial evolution of magnetic fluctuations within the dissipation range, right after the high-frequency spectral break, employing observations by Messenger and Wind of the same fast wind stream during a radial alignment. The same event has already been considered in literature to show, for the first time, that the high-frequency break separating the fluid from the kinetic regime moves to lower frequency as the wind expands. The present work aims to analyze the nature of the high-frequency magnetic fluctuations beyond the spectral break and show that their character is compatible with left-hand, outward-propagating, ion cyclotron waves and right-hand kinetic Alfv\acute{e}n waves. It is also shown that the low-frequency limit of these fluctuations follows the radial evolution of the spectral break, which also reflects in the behavior of their intermittency character. Finally, the total power and the compressive character of these two wave populations are analyzed and compared as a function of the heliocentric distance, leading us to conclude that the overall picture is in favor of a radial decrease.
Volume
805
Issue
1
Start page
46
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...805...46T
Rights
open.access
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