  The breakup pathway of the Rayleigh fission process observed experimentally
using high-speed imaging of a charged drop levitated in an AC quadrupole trap
is shown to undergo asymmetric breakup by ejecting a jet in the upward
direction ((i.e., opposite to the direction of gravity)). To explain this
typical experimental observation, we carry out numerical calculations based on
the boundary element method considering inertial droplets levitated
electrodynamically using quadrupole electric fields. The simulations show that
the gravity-induced downward shift in the equilibrium position of the drop in
the trap causes significant, large-amplitude shape oscillations superimposed
over the center-of-mass oscillations of the drop. An important observation here
is that the shape oscillations due to the applied quadrupole fields, result in
sufficient deformations that act as triggers for the onset of the instability
below the Rayleigh limit, thereby admitting a sub-critical instability. The
center-of-mass oscillations of the droplet within the trap, which follow the
applied frequency, are out of phase with the applied AC signal. Thus the
combined effect of shape deformations and dynamic position of the drop leads to
an asymmetric breakup such that the Rayleigh fission occurs upwards via the
ejection of a jet at the north-pole of the deformed drop.
