Mechanisms of generation and statistical properties of whistler waves in the solar wind

The mechanisms of generation and properties of whistler waves in the solar wind have remained poorly understood until recently. The recent analysis of simultaneous wave and particle measurements aboard ARTEMIS spacecraft have allowed us to make some progress in understanding whistler wave properties and generation mechanisms in the solar wind. First, using measurements in the particle burst mode we have directly demonstrated for several events that the whistler heat flux instability indeed operates in the solar wind and generates the quasi-parallel whistler waves observed in the solar wind. Second, using continuously available magnetic field spectra measured over 3 years (2010-2013) we have determined whistler wave occurrence and properties (amplitudes, frequency, frequency bandwidth, obliqueness) and demonstrated their correlations with various macroscopic plasma parameters (electron heat flux, electron beta parameter and electron temperature anisotropy). Based on the statistical study we discuss the generation mechanism of the whistler waves and their role in scattering suprathermal electrons and electron heat flux regulation in the solar wind.