  Ellerman bombs (EBs) and Ultraviolet (UV) bursts are common brightening
phenomena which are usually generated in the low solar atmosphere of emerging
flux regions. In this paper, we have investigated the emergence of an initial
un-twisted magnetic flux rope based on three-dimensional (3D)
magneto-hydrodynamic (MHD) simulations. The EB-like and UV burst-like
activities successively appear in the U-shaped part of the undulating magnetic
fields triggered by Parker Instability. The EB-like activity starts to appear
earlier and lasts for about 80 seconds. Six minutes later, a much hotter UV
burst-like event starts to appear and lasts for about 60 seconds. Along the
direction vertical to the solar surface, both the EB and UV burst start in the
low chromosphere, but the UV burst extends to a higher altitude in the up
chromosphere. The regions with apparent temperature increase in the EB and UV
burst are both located inside the small twisted flux ropes generated in
magnetic reconnection processes, which are consistent with the previous 2D
simulations that most hot regions are usually located inside the magnetic
islands. However, the twisted flux rope corresponding to the EB is only
strongly heated after it floats up to an altitude much higher than the
reconnection site during that period. Our analyses show that the EB is heated
by the shocks driven by the strong horizontal flows at two sides of the
U-shaped magnetic fields. The twisted flux rope corresponding to the UV burst
is heated by the driven magnetic reconnection process.
