  Jupiter's tenuous dust ring system is embedded in the planet's inner
magnetosphere, and - among other structures - contains a very tenuous
protrusion called the Thebe extension. In an attempt to explain the existence
of this swath of particles beyond Thebe's orbit, Hamilton and Kr\"uger (2008)
proposed that the dust particle motion is driven by a shadow resonance caused
by variable dust charging on the day and night side of Jupiter. However, the
model by Divine (1983) together with recent observations by the Juno spacecraft
indicates a warm and rather dense inner magnetosphere of Jupiter which implies
that the mechanism of the shadow resonance does not work. Instead we argue that
dust grains ejected from Thebe due to micrometeoroid bombardment become the
source of dust in the Thebe extension. We show that large (grain radii of a few
micrometers up to multi-micrometers) charged dust grains having significant
initial velocities oscillate in the Thebe extension. Smaller charged grains
(with sub-micrometer radii) ejected from Thebe do not spend much time in the
Thebe extension and migrate into the Thebe ring. At the same time, if such
grains are ejected from larger dust grains in the Thebe extension due to
fragmentation, they continue to oscillate within the Thebe extension for years.
We argue that fragmentation of large dust grains in the Thebe extension could
be the main source of sub-micrometer grains detected in the Thebe extension.
