``Bumpy" cislunar magnetotail and its mapping to LEO

Many magnetotail tearing-stability analyses assume an equatorial $B_z$ profile that is constant or decreases monotonically tailward. Recent empirical reconstructions instead suggest multiple $B_z$ ridges during the substorm growth phase. Here we investigate the formation and evolution of such bumpy profiles in the entire cislunar tail using the data-mining algorithm ARGUS (AI-based Reconstruction of the Geospace Unified System) and compare its reconstructions with the low Earth orbit (LEO) observations of trapped and precipitating electron fluxes made by the Electron Losses and Fields Investigation (ELFIN) mission. It is shown that multiple $B_z$ ridges appear in the substorm growth phase soon after the southward turning of the interplanetary magnetic field, and they remain stagnant for about half an hour prior to the onset, resembling the conventional tail disturbed by a tearing mode with a wavelength of $\sim 15 R_E$ ($R_E$ being the Earth's radius). The dipolarization after the onset appears as part of the evolution of this global tearing-like perturbation of the equatorial magnetic field, associated with the enhanced earthward flux transfer. This bumpy structure is consistent with the ELFIN observations of depletions of the ratio between precipitating and trapped fluxes of energetic electrons.