  Coronal loops are building blocks of solar active regions. However, their
formation mechanism is still not well understood. Here we present direct
observational evidence for the formation of coronal loops through magnetic
reconnection as new magnetic fluxes emerge into the solar atmosphere.
Extreme-ultraviolet observations of the Atmospheric Imaging Assembly (AIA)
onboard the Solar Dynamics Observatory (SDO) clearly show the newly formed
loops following magnetic reconnection within a plasma sheet. Formation of the
loops is also seen in the h{\alpha} line-core images taken by the New Vacuum
Solar Telescope. Observations from the Helioseismic and Magnetic Imager onboard
SDO show that a positive-polarity flux concentration moves towards a
negative-polarity one with a speed of ~0.4 km/s, before the formation of
coronal loops. During the loop formation process, we found signatures of flux
cancellation and subsequent enhancement of the transverse field between the two
polarities. The three-dimensional magnetic field structure reconstructed
through a magnetohydrostatic model shows field lines consistent with the loops
in AIA images. Numerous bright blobs with an average width of 1.37 Mm appear
intermittently in the plasma sheet and move upward with a projected velocity of
~114 km/s. The temperature, emission measure and density of these blobs are
about 3 MK, 2.0x10^(28) cm^(-5) and 1.2x10^(10) cm^(-3), respectively. A power
spectral analysis of these blobs indicates that the observed reconnection is
likely not dominated by a turbulent process. We have also identified flows with
a velocity of 20 to 50 km/s towards the footpoints of the newly formed coronal
loops.

Solar and Stellar Astrophysics