Observation of Acceleration of HI Clouds Within the Fermi Bubbles
  The ~200 HI clouds observed to be entrained in the Fermi Bubble wind show a
trend of increasing maximum |VLSR| with Galactic latitude. We analyze previous
observations and present new data from the Green Bank Telescope that rule out
systematic effects as the source of this phenomenon. Instead, it is likely
evidence for acceleration of the clouds. The data suggest that clouds in the
lower 2 kpc of the Fermi Bubbles, within the Bubble boundaries established from
X-ray studies, have an outflow velocity that rises from ~150 - 200 km/s close
to the Galactic Center and reaches ~330 km/s at a distance of 2.5 - 3.5 kpc.
These parameters are also consistent with the kinematics of UV absorption lines
from highly ionized species observed against two targets behind the Fermi
Bubbles at $b = -6.6^{\circ}$, and $b = +11.2^{\circ}$. The implied neutral
cloud lifetime is 4 - 10 Myr.
