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Features of the streamer-corona discharge and the NO processing area in corona radical shower system was studied experimentally. The time evolution of the streamer-corona discharges induced by laser irradiations was measured to understand the discharge characteristics responsible for NO removal. Using the wide-range planar laser-induced fluorescence imaging (image size: 240 mm in width and 35 mm in height), two-dimensional distributions of ground-state NO were observed not only at the discharge zone but also both the downstream and the upstream regions of the reactor. The obtained results showed that the density of NO molecules decreased not only in the plasma region formed by the corona streamers and downstream region of the reactor but also in the upstream region of the reactor. In the present reactor at low main gas flow rate, it was considered that electrohydrodynamic (EHD) flow became to be dominant, and the flow toward the upstream affected the decrease of NO in the upstream region. As the EHD-induced secondary flow is correlated with the current flow from the stressed electrode to grounded electrode, the control of the streamers seems to be an important factor for optimizing the reactors used for NOx removal.