THEMIS/ARTEMIS Observations of Kinetic-Scale Turbulence in the Solar Wind: Analysis of Electric and Magnetic Field Fluctuations

We present an analysis of kinetic-scale electromagnetic fluctuations in the solar wind using data from THEMIS and ARTEMIS spacecraft. We examine high time-resolution electric and magnetic field measurements in Fast Survey (up to 4 samples/second) and Particle Burst (up to 128 samples/second) modes during two carefully selected periods of observation in the quiet solar wind. We discuss the meticulous analysis process, which includes characterization and removal of instrumental effects and noise sources affecting the electric and magnetic field data at the scales of interest. Our primary interest is in measurements above 0.1 Hz or so, roughly corresponding to the breakpoint where the so-called dissipation range of solar wind turbulence begins. After cleaning the data and eliminating spurious effects, we compute parameters such as the electric to magnetic field ratio, the magnetic compressibility, magnetic helicity, and other relevant quantities in order to diagnose the nature of the fluctuations at scales between the ion and electron cyclotron frequencies. This allows us to extract information on the dominant modes composing the fluctuations. We also discuss the presence and role of coherent structures in the measured fluctuations. The nature of the fluctuations in the dissipation or dispersive scales of solar wind turbulence is still debated. This observational study is highly relevant to the current Turbulent Dissipation Challenge.