Observations of discrete harmonics emerging from equatorial noise

0446376 - ÚFA 2016 RIV GB eng J - Journal Article
Balikhin, M. A. - Shprits, Y. Y. - Walker, S. N. - Chen, L. - Cornilleau-Wehrlin, N. - Dandouras, I. - Santolík, Ondřej - Carr, C. - Yearby, K. H. - Weiss, B.
Observations of discrete harmonics emerging from equatorial noise.
Nature Communications. Roč. 6, Article number: 7703 (2015), s. 1-6. E-ISSN 2041-1723
R&D Projects: GA MŠMT LH12231
Institutional support: RVO:68378289
Keywords : cluster * magnetosphere * frequency * proton * waves * mode
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 11.329, year: 2015
http://www.nature.com/ncomms/2015/150714/ncomms8703/abs/ncomms8703.html

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.
Permanent Link: http://hdl.handle.net/11104/0248378