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Ultraviolet (UV) bursts and Ellerman bombs (EBs) are small-scale magneticreconnection events taking place in the highly stratified, low solaratmosphere. It is still not clear whether UV bursts have to be generated at ahigher atmospheric layer than EBs or whether both UV bursts and EBs can occurin the low chromosphere. We numerically studied the low $\beta$ magneticreconnection process around the solar temperature minimum region (TMR). Thetime-dependent ionization degrees of hydrogen and helium are included in theMHD code, which lead to a more realistic magnetic diffusion caused byelectron-neutral collision and ambipolar diffusion. A more realistic radiativecooling model from Carlsson & Leenaarts 2012 is included in the simulations.Our results in high resolution indicate that the plasmas in the reconnectionregion are heated up to more than $20,000$ K if the reconnecting magnetic fieldis as strong as $500$ G, which suggests that UV bursts can be generated in thedense low chromosphere. The dominant mechanism for producing the UV burst inthe low chromosphere is heating, as a result of the local compression in thereconnection process. The thermal energy occurring in the reconnection regionrapidly increases after the turbulent reconnection mediated by plasmoids isinvoked. The average power density of the generated thermal energy in thereconnection region can reach over $1000$ erg cm$^{-3}$ s$^{-1}$, which iscomparable to the average power density accounting for a UV burst. With thestrength of the reconnecting magnetic field exceeding $900$ G, the width of thesynthesized Si IV 1394 A line profile with multiple peaks can reach up to $100$km s$^{-1}$, which is consistent with observations.

Plausibility of ultraviolet burst generation in the low solar chromosphere