On the generation of proton beams in fast solar wind in the presence of obliquely propagating Alfvén waves

• Published in: Journal of Geophysical Research: Space Physics Vol. 115; no. A5
• Main Authors: Osmane, A., Hamza, A. M., Meziane, K.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.05.2010; American Geophysical Union
• Subjects: Astrophysics; Cores; distribution functions; Earth sciences; Earth, ocean, space; Exact sciences and technology; Planetology; Plasma physics; solar wind; Space; Wave propagation; wave/particle interaction; satellites; models; Plasma; density; Space remote sensing; Satellite observation; Wave interaction; Dynamical system; velocity; solar wind; drill cores; Proton beam; Wave propagation; solution; Alfven wave; Distribution function; temperature; ions; Particle wave interaction; inclusions; theory
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2169-9402
• DOI: 10.1029/2009JA014655

Over the past few decades, satellite investigations have revealed that the solar wind contains a plethora of distribution function signatures (proton beam, anisotropic cores) requiring models departing from the conventional fluid theory and necessitating the inclusion of wave‐particle interactions. Numerous theoretical models and explanations have been proposed, but several questions concerning time and heliocentric evolution as well as the formation of beam components and anisotropic cores remain unanswered. We propose a simple solution for the generation of beam components, as a result of physical trapping due to obliquely propagating Alfvén modes, based on a previously reported dynamical system describing the wave interaction with a single ion in the absence of dissipation mechanisms. We have found that beams with significant densities (7%–8%) and with velocities of the order of the Alfvén speed can be generated. The beams' properties, including density, velocity, and temperature, are dependent on the wave propagation angle. The results are in qualitative agreement with the observations and could provide an explanation for the evolution of nonthermal distribution functions observed in fast solar wind and other space plasmas regimes.