Cold Ion Energization by Secondary Magnetic Reconnection in a Turbulent Reconnection Jet During Storm Period

During geomagnetic storms, cold ions from the ionosphere substantially contribute to the plasma sheet population, which may significantly impact magnetotail energy conversion and transport. However, the energization of cold ions in the magnetotail during storm periods remains poorly understood. This paper investigates cold ion energization by secondary reconnection in a magnetotail reconnection outflow during a storm period. This secondary reconnection was triggered by the interaction between a large-scale flux pileup region and a magnetic flux rope. Cold protons originating from the ionosphere were injected into the diffusion region from the lobe region. These cold protons gained energy mainly through the normal electric field in the flux pileup region before entering the cold ion diffusion region, where their bulk kinetic energy was mainly converted into thermal kinetic energy. These results will significantly advance our understanding of the energization and transport of cold ions in the magnetotail.