Abstract. This paper reviews recent aspects of solar wind physics and elucidates the
role Alfvén waves play in solar wind acceleration and turbulence, which
prevail in the low corona and inner heliosphere. Our understanding of the
solar wind has made considerable progress based on remote sensing, in situ
measurements, kinetic simulation and fluid modeling. Further insights are
expected from such missions as the Parker Solar Probe and Solar Orbiter. The sources of the solar wind have been identified in the chromospheric
network, transition region and corona of the Sun. Alfvén waves excited by
reconnection in the network contribute to the driving of turbulence and
plasma flows in funnels and coronal holes. The dynamic solar magnetic field
causes solar wind variations over the solar cycle. Fast and slow solar wind
streams, as well as transient coronal mass ejections, are generated by the
Sun's magnetic activity. Magnetohydrodynamic turbulence originates at the Sun and evolves into
interplanetary space. The major Alfvén waves and minor magnetosonic waves,
with an admixture of pressure-balanced structures at various scales,
constitute heliophysical turbulence. Its spectra evolve radially and develop
anisotropies. Numerical simulations of turbulence spectra have reproduced key
observational features. Collisionless dissipation of fluctuations remains a
subject of intense research. Detailed measurements of particle velocity distributions have revealed
non-Maxwellian electrons, strongly anisotropic protons and heavy ion beams.
Besides macroscopic forces in the heliosphere, local wave–particle
interactions shape the distribution functions. They can be described by the
Boltzmann–Vlasov equation including collisions and waves. Kinetic simulations
permit us to better understand the combined evolution of particles and waves
in the heliosphere.
Perpendicular Ion Heating by Cyclotron Resonant Dissipation of Turbulently Generated Kinetic Alfvén Waves in the Solar Wind