  Small-scale ephemeral coronal holes may be a recurring feature on the solar
disk, but have received comparatively little attention. These events are
characterized by compact structure and short total lifetimes, substantially
less than a solar disk crossing. We present a systematic search for these
events, using Atmospheric Imaging Assembly EUV image data from the Solar
Dynamics Observatory, covering the time period 2010 - 2015. Following strict
criteria, this search yielded four clear examples of the ephemeral coronal hole
phenomenon. The properties of each event are characterized, including their
total lifetime, growth and decay rates, and areas. The magnetic properties of
these events are also determined using Helioseismic and Magnetic Imager data.
Based on these four events, ephemeral coronal holes experience rapid initial
growth of up to 3000 Mm2/hr, while the decay phases are typically more gradual.
Like conventional coronal holes, the mean magnetic field in each ephemeral
coronal hole displays a consistent polarity, with mean magnetic flux densities
generally < 10 G. No evidence of a corresponding signature is seen in solar
wind data at 1 AU. Further study is needed to determine whether ephemeral
coronal holes are under-reported events or a truly rare phenomenon.
