Two modes of carbonaceous dust alignment
  Radiative Torques (RATs) or Mechanical Torques (METs) acting on irregular
grains can induce the alignment of dust grains in respect to the alignment axis
(AA), which can be either the direction of the magnetic field, or the direction
of the radiation. We show that carbonaceous grains can be aligned with their
axes both parallel and perpendicular to the AA and we explore the conditions
where the particular mode of alignment takes place. We identify a new process
of alignment of charged carbonaceous grains in a turbulent magnetized
interstellar medium with respect to an electric field. This field acts on
grains accelerated in a turbulent medium and gyro-rotating about a magnetic
field. The electric field can also arise from the temporal variations of
magnetic field strength in turbulent compressible media. The direction of the
electric field is perpendicular to a magnetic field and the carbonaceous grains
precess in the electric field because of their electric moments. If this
precession is faster than Larmor precession in the magnetic field, the
alignment of such grains is with their long axes parallel to magnetic field. We
explore the parameter space for which the new mechanism aligns grains with long
axes parallel to the magnetic field. We compare this mechanism with another
process that provides the same type of alignment, namely, the RAT alignment of
grains with insufficiently fast internal relaxation. We describe the conditions
for which the particular mode of carbonaceous grain alignment is realized and
discuss what information can be obtained by measuring the resulting
polarization.
