Whistler mode waves and the electron heat flux in the solar wind: Cluster observations

0434919 - ÚFA 2015 RIV US eng J - Journal Article
Lacombe, C. - Alexandrova, O. - Matteini, L. - Santolík, Ondřej - Cornilleau-Wehrlin, N. - Mangeney, A. - De Conchy, Y. - Maksimovic, M.
Whistler mode waves and the electron heat flux in the solar wind: Cluster observations.
Astrophysical Journal. Roč. 796, č. 1 (2014), s. 1-11. ISSN 0004-637X. E-ISSN 1538-4357
R&D Projects: GA ČR GAP205/10/2279; GA MŠMT LH12231
Institutional support: RVO:68378289
Keywords : solar wind * turbulence * waves
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 5.993, year: 2014
http://iopscience.iop.org/0004-637X/796/1/5/article

The nature of the magnetic field fluctuations in the solar wind between the ion and electron scales is still under debate. Using the Cluster/STAFF instrument, we make a survey of the power spectral density and of the polarization of these fluctuations at frequencies f ϵ [1, 400] Hz, during five years (2001–2005), when Cluster was in the free solar wind. In ~ 10% of the selected data, we observe narrowband, right-handed, circularly polarized fluctuations, with wave vectors quasi-parallel to the mean magnetic field, superimposed on the spectrum of the permanent background turbulence. We interpret these coherent fluctuations as whistler mode waves. The lifetime of these waves varies between a few seconds and several hours. Here, we present, for the first time, an analysis of long-lived whistler waves, i.e., lasting more than five minutes. We find several necessary (but not sufficient) conditions for the observation of whistler waves, mainly a low level of background turbulence, a slow wind, a relatively large electron heat flux, and a low electron collision frequency. When the electron parallel beta factor βeǁ is larger than 3, the whistler waves are seen along the heat flux threshold of the whistler heat flux instability.
Permanent Link: http://hdl.handle.net/11104/0238882