Crater Structure Behind Reconnection Front.

Magnetic reconnection is the physical process that converts the energy from the fields to the plasmas in space, astrophysical and laboratory plasmas. The Reconnection front (RF) is the structure generated in the reconnection outflow region and participates in the energy release budget. Here, we first report a novel crater structure of magnetic field behind the RF, which is well supported by both the in‐situ observations from the Magnetospheric Multiscale mission and kinetic particle‐in‐cell simulations. The theoretical explanations from the simulations suggests that the formation of the crater structure is possibly due to that high‐speed outflow electron jet from inner electron diffusion region constantly strikes the RF. From another perspective, the crater structure is the continuous impact of the electron jet. Our results can establish a new understanding of the RF and energy conversion during magnetic reconnection. Plain Language Summary: Magnetic reconnection is a natural process in space environments, astrophysical settings, and laboratories, where energy from magnetic fields is transformed into the energy of various particles. One crucial structure in this process is called the reconnection front (RF), which plays a big role in how energy is released. In our study, we have discovered something interesting: a unique crater‐like structure behind the RF. We found evidence for this in observations from the Magnetospheric Multiscale mission and computer simulations that study the behavior of particles in magnetic reconnection. Our simulations suggest that this crater shape happens because electrons have the high‐speed outflow and form current jets. It is like the electrons poured out from the inner electron diffusion region, hitting a speed bump. Another way to think about it is that this crater is formed by the continuous impact of fast‐outflowing electron jets. Understanding this crater structure helps us better grasp how the RF works and how energy changes during magnetic reconnection. Our research finds and tries to explain a new piece of the puzzle in understanding the mysteries of space and plasmas in the magnetic reconnection process. Key Points: A novel crater structure is first verified behind the Reconnection front (RF) by both Magnetospheric Multiscale observations and particle‐in‐cell simulationsThe formation of the crater structure appears to be associated with the high‐speed electron jets from inner electron diffusion regionA possible scenario that electron outflow constantly strikes the RF and then causes the formation of the crater structure [ABSTRACT FROM AUTHOR]