When a passive electric antenna is immersed in a stable plasma, the thermal motion of the ambient particles produces electrostatic fluctuations, which are completely determined by the particle velocity distributions. A sensitive and well-calibrated receiver connected to a wire dipole antenna can measure these electric field oscillations, and turning them into spectra. The analysis of the voltage power spectrum, known as the method of quasi-thermal noise spectroscopy (QTN), gives an accurate diagnostics for in-situ electron parameters, mainly the density and the core temperature, as well as an estimation of suprathermal electron properties, in various space media. Since particles velocity distributions functions in collisionless plasmas usually exhibit important deviation from the equilibrium Maxwellian distribution function, in magnetized plasmas, this deviation from equilibrium is often observed as an anisotropy of the distribution in the direction parallel and perpendicular to the local magnetic field. Moreover, a strahl population (electron beam aligned with the local magnetic field) is of importance, especially close to the Sun.

In this context, this brainstorming is mostly dedicated to the study of the electron suprathermal particles in the solar wind from the QTN method.
We will first work on recent studies on QTN from WIND/WAVES data, taking into account the angle between the antenna and the solar wind speed on the proton thermal noise. We will then focus on the anisotropy determination and discuss implications for applying the QTN method for future solar wind and coronal exploration missions Solar Orbiter and Solar Probe Plus.