  The inverse Evershed flow (IEF) is an inflow of material into the penumbra of
sunspots in the solar chromosphere that occurs along dark, elongated
superpenumbral fibrils extending from about the outer edge of the moat cell to
the sunspot. The IEF channels exhibit brightenings in the penumbra, where the
supersonic IEF descends to the photosphere causing shock fronts with localized
heating. We used an 1-hr time-series of spectroscopic observations of the
chromospheric spectral lines of CaIIIR at 854nm and H$\alpha$ at 656nm taken
with IBIS at the DST to investigate the temporal evolution of IEF channels.
Complementary information on the photospheric magnetic field was obtained from
observations with FIRS at 1083\nm and HMI. We find that individual IEF channels
are long-lived (10-60min) and only show minor changes in position and flow
speed during their life time. Initiation and termination of IEF channels takes
several minutes. The IEF channels with line-of-sight velocities of about 10km/s
show no lasting impact from transient or oscillatory phenomena with maximal
velocity amplitudes of only about 1km/s that run along them. We could not
detect any clear correlation of the location and evolution of IEF channels to
local magnetic field properties in the photosphere in the penumbra or moving
magnetic features in the sunspot moat. Our results support a picture of the IEF
as a field-aligned siphon flow along arched loops. From our data we cannot
determine if their evolution is controlled by events at the outer end in the
moat or at the inner end in the penumbra.
