  The process of particle acceleration by left-hand, circularly polarised
inertial Alfven waves (IAW) in a transversely inhomogeneous plasma is studied
using 3D particle-in-cell simulation. A cylindrical tube with, transverse to
the background magnetic field, inhomogeneity scale of the order of ion inertial
length is considered on which IAWs with frequency $0.3 \omega_{ci}$ are
launched that are allowed to develop three wavelength. As a result time-varying
parallel electric fields are generated in the density gradient regions which
accelerate electrons in the parallel to magnetic field direction. Driven
perpendicular electric field of IAWs also heats ions in the transverse
direction. Such numerical setup is relevant for solar flaring loops and earth
auroral zone. This first, 3D, fully-kinetic simulation demonstrates electron
acceleration efficiency in the density inhomogeneity regions, along the
magnetic field, of the order of 45% and ion heating, in the transverse to the
magnetic field direction, of 75%. The latter is a factor of two times higher
than the previous 2.5D analogous study and is in accordance with solar flare
particle acceleration observations. We find that the generated parallel
electric field is localised in the density inhomogeneity region and rotates in
the same direction and with the same angular frequency as the initially
launched IAW. Our numerical simulations seem also to suggest that the "knee"
often found in the solar flare electron spectra can alternatively be
interpreted as the Landau damping (Cerenkov resonance effect) of IAWs due to
the wave-particle interactions.
