A Remote Brightening from Interactions between an Extreme-ultraviolet Jet and a Magnetic Null

Remote brightening (RB) refers to brightening at a footpoint of magnetic loops in the solar atmosphere, which is passively triggered by an eruption occurring at the other footpoint. Here, we present observations of an RB event driven by an extreme-ultraviolet (EUV) jet. The leading front of the jet exhibits flows exceeding the characteristic sound speed, and it triggers RBs at two remote sites that are connected by coronal loops. We focus on the RB that occurred at one of the footpoints, in which the magnetic structure is characterized by a dome-like feature with magnetic null points. When the jet propagates to this footpoint, the brightening displays a distinct inverted-Y-shaped structure. Bidirectional flows with a velocity of about 30 km s⁻¹ are detected in any two branches of this structure, which are suggestive of the occurrence of magnetic reconnection at this footpoint. To investigate the physics of the interaction between the jet and the remote magnetic null point, we conducted a 2D MHD simulation with adaptive mesh refinement. We find that the collapse of the magnetic null point is induced by a fast-mode wave, and the flow associated with the jet elongates the current sheet, thereby triggering plasmoid instability. Subsequent magnetic reconnection not only forms the bright inverted-Y-shaped structure but also drives bidirectional flows along the structures, being consistent with the observational findings. This study provides new insights into the dynamic interaction between EUV jets and remote magnetic nulls in the solar atmosphere, and helps understand the diverse natures of RBs.