  We report both decreasing and increasing trends in the patch sizes during
pulsating aurora events. About 150 pulsating auroral events over the
Fennoscandian Lapland have been successfully analyzed for their average patch
size, total patch area, and number of patches as a function of event time,
typically 1-2 hr. An automatic routine has been developed to detect patches in
the all-sky camera images. In addition to events with decreasing and increasing
average patch size evolution over the course of the pulsating aurora, events
with no size trends and events with intermittently increasing and decreasing
patch size trends were also found. In this study, we have analyzed a subset of
events for which the average and total patch size systematically increase or
decrease. The events with increasing patch size trend do not experience a
decrease in the peak emission height, which was previously associated with the
behavior of pulsating aurora precipitation. Furthermore, the events with
increasing patch sizes have shorter lifetimes and twice as many
substorm-injected energetic electrons at geosynchronous orbit as the events
with decreasing patch sizes. Half of the events with increasing patch sizes
occur during substorm expansion phases, while a majority (64%) of the ones with
decreasing patch sizes take place during the recovery phase. These findings
suggest that the visual appearance of pulsating aurora may be used as an
indication of the pulsating aurora energy deposition to the atmosphere.
