Measuring the magnetic structure velocity for the 11 July 2017 magnetotail reconnection event

Velocities in magnetic reconnection events, such as those of particles, are best understood in the frame of reference of the magnetic structure that is ultimately responsible for the reconnection process. We discuss four different methods for evaluating the velocity of the magnetic structure, and use those methods to find the magnetic structure velocity for the 11 July 2017 magnetotail reconnection event studied by Torbert et al. (Science, 2018). The four methods are timing analysis, the SpatioTemporal Difference (STD) method of Shi et al. (JGR, 2006), Electron Magnetohydrodynamic (EMHD) reconstruction (Sonnerup et al., JGR, 2016), and polynomial reconstruction of the magnetic field in the vicinity of the spacecraft using the magnetic field and particle current density as input to the model. The relative merits of the different techniques will be discussed, and the different results compared.