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Abstract

Due to its collisionless nature, the solar wind presents significant kinetic characteristics, which make it ideally suited to be modelled by Particle-In-Cell (PIC) codes. We resort to the use of semi-implicit PIC codes, which allow the coupling in a simulation of significantly different spatial and temporal scales, to model particle velocity distribution functions (VDFs) commonly observed in the near-Sun solar wind. The multiplicity of scales in the solar wind considerably complicates our understanding of the physical phenomena that govern its dynamics as it propagates through interplanetary space. We shed light on some of them, always focusing on the kinetic aspects of the solar wind. Specifically, we show how the interaction between whistler waves and electron VDFs affect the heat flux transported by the solar wind.We present results of simulations conducted to study the interplay between the macroscopic expansion of the solar wind and the microscopic kinetic instabilities that are of great significance in shaping electron VDFs. We finally describe how we model the signature of the Sun’s electric potential: the sunward electron deficit. The numerical results are contextualised in the framework of recent observations and supported by theoretical studies.