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Observations of discrete harmonics emerging from equatorial noise

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Title: Observations of discrete harmonics emerging from equatorial noise
Authors: Balikhin, MA
Shprits, YY
Walker, SN
Chen, L
Cornilleau-Wehrlin, N
Dandouras, I
Santolik, O
Carr, C
Yearby, KH
Weiss, B
Item Type: Journal Article
Abstract: A number of modes of oscillations of particles and fields can exist in space plasmas. Since the early 1970s, space missions have observed noise-like plasma waves near the geomagnetic equator known as 'equatorial noise'. Several theories were suggested, but clear observational evidence supported by realistic modelling has not been provided. Here we report on observations by the Cluster mission that clearly show the highly structured and periodic pattern of these waves. Very narrow-banded emissions at frequencies corresponding to exact multiples of the proton gyrofrequency (frequency of gyration around the field line) from the 17th up to the 30th harmonic are observed, indicating that these waves are generated by the proton distributions. Simultaneously with these coherent periodic structures in waves, the Cluster spacecraft observes 'ring' distributions of protons in velocity space that provide the free energy for the waves. Calculated wave growth based on ion distributions shows a very similar pattern to the observations.
Issue Date: 14-Jul-2015
Date of Acceptance: 1-Jun-2015
URI: http://hdl.handle.net/10044/1/25476
DOI: 10.1038/ncomms8703
ISSN: 2041-1723
Publisher: Nature Publishing Group
Journal / Book Title: Nature Communications
Volume: 6
Copyright Statement: © 2015, Rights Managed by Nature Publishing Group
Sponsor/Funder: Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council [2006-2012]
Science and Technology Facilities Council (STFC)
Funder's Grant Number: ST/K001051/1
ST/N002784/1
ST/L001276/1
ST/M003116/1
ST/G008272/1
ST/H00419X/1
ST/I000623/1
ST/J004553/1
ST/K001051/1
ST/H002383/1
Keywords: Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
CLUSTER
MAGNETOSPHERE
PROTON
Publication Status: Published
Article Number: ARTN 7703
Appears in Collections:Space and Atmospheric Physics
Physics
Faculty of Natural Sciences