  Previous studies of phase mixing of ion cyclotron (IC), Alfv\'enic, waves in
the collisionless regime have established the generation of parallel electric
field and hence acceleration of electrons in the regions of transverse density
inhomogeneity. However, outstanding issues were left open. Here we use 2.5D,
relativistic, fully electromagnetic PIC (Particle-In-Cell) code and an analytic
MHD (Magnetohydrodynamic) formulation, to establish the following points: (i)
Using the generalised Ohm's law we find that the parallel electric field is
supported mostly by the electron pressure tensor, with a smaller contribution
from the electron inertia term. (ii) The generated parallel electric field and
the fraction of accelerated electrons are independent of the IC wave frequency
remaining at a level of six orders of magnitude larger than the Dreicer value
and approximately 20% respectively. The generated parallel electric field and
the fraction of accelerated electrons increase with the increase of IC wave
amplitude. The generated parallel electric field seems to be independent of
plasma beta, while the fraction of accelerated electrons strongly increases
with the decrease of plasma beta (for plasma beta of 0.0001 the fraction of
accelerated electrons can be as large as 47%). (iii) In the collisionless
regime IC wave dissipation length (that is defined as the distance over which
the wave damps) variation with the driving frequency shows a deviation from the
analytical MHD result, which we attribute to a possible frequency dependence of
the effective resistivity. (iv) Effective anomalous resistivity, inferred from
our numerical simulations, is at least four orders of magnitude larger than the
classical Spitzer value.
