  Recently, a transient localized brightness enhancement has been observed in
Jupiter's main auroral emission close to noon by Palmaerts et al. (2014). We
use results from three-dimensional global MHD simulations to understand what is
causing this localized peak in the main emission. In the simulations, the peak
occurs every rotation period and is due to shearing motions in the magnetodisk.
These shearing motions are caused by heavy flux-tubes being accelerated to
large azimuthal speeds at dawn. The centrifugal force acting on these
flux-tubes is then so high that they rapidly move away from the planet. When
they reach noon, their azimuthal velocity decreases, thus reducing the
centrifugal force, and allowing the flux-tubes to move back closer to Jupiter.
The shearing motions associated with this periodic phenomenon locally increase
the field aligned currents in the simulations, thus causing a transient
brightness enhancement in the main auroral emission, similar to the one
observed by Palmaerts et al. (2014).
