  We present a method that isolates time-varying components from coronagraph
and EUV images, allowing sub-streamer transients propagating within streamers
to be tracked from the low to high corona. The method uses a temporal bandpass
filter with a transmission bandwidth of ~2.5-10 hours that suppresses both high
and low frequency variations in observations made by the STEREO/SECCHI suite.
We demonstrate that this method proves crucial in linking the low corona where
the magnetic field is highly non-radial, to their counterparts in the high
corona where the magnetic field follows a radial path through the COR1
instrument. We also applied our method to observations by the COR2 and EUVI
instruments onboard SECCHI and produced height-time profiles that revealed
small density enhancements, associated with helmet streamers, propagating from
~1.2 Rs out to beyond 5 Rs. Our processing method reveals that these features
are common during the period of solar minimum in this study. The features recur
on timescales of hours, originate very close to the Sun, and remain coherent
out into interplanetary space. We measure the speed of the features and
classify them as: slow (a few to tens of km/s) and fast (~100 km/s). Both types
of features serve as an observable tracer of a variable component of the slow
solar wind to its source regions. Our methodology helps overcome the
difficulties in tracking small-scale features through COR1. As a result, it
proved successful in measuring the connectivity between the low and high corona
and in measuring velocities of small-scale features.
