  Emerging dimming occurs in isolated solar active regions (ARs) during the
early stages of magnetic flux emergence. Observed by the Atmospheric Imaging
Assembly, it features a rapid decrease in extreme-ultraviolet (EUV) emission in
the 171 \r{A} channel images, and a simultaneous increase in the 211 \r{A}
images. Here, we analyze the coronal thermodynamic and magnetic properties to
probe its physical origin. We calculate the time-dependent differential
emission measures for a sample of 18 events between 2010 and 2012. The emission
measure (EM) decrease in the temperature range $5.7 \le \log_{10}T \le 5.9$ is
well correlated with the EM increase in $6.2 \le \log_{10}T \le 6.4$ over eight
orders of magnitude. This suggests that the coronal plasma is being heated from
the quiet-Sun, sub-MK temperature to 1-2 MK, more typical for ARs. Potential
field extrapolation indicates significant change in the local magnetic
connectivity: the dimming region is now linked to the newly emerged flux via
longer loops. We conclude that emerging dimming is likely caused by coronal
heating episodes, powered by reconnection between the emerging and the ambient
magnetic fields.
