Relation between cusp ion structures and dayside reconnection for four IMF clock angles: OpenGGCM‐LTPT results

Abstract

AbstractWhen, where, and which type of reconnection (antiparallel or component) happens on the dayside magnetopause are long‐standing unsolved questions due to insufficient in situ observation of reconnection sites. Previous studies showed that the dispersed ion signatures observed in the magnetospheric cusps depend on the reconnection mechanism, suggesting that cusp ion signatures can be a good tool to investigate the locations and properties of dayside reconnection. We investigate this close relation between cusp signatures and magnetopause reconnection for four different interplanetary magnetic field (IMF) clock angles (CA) using the Open Global Geospace Circulation Model (OpenGGCM) and the Liouville Theorem Particle Tracer(LTPT). OpenGGCM produces dayside reconnection under the resistive MHD theory, and LTPT calculates cusp ion signatures caused by the simulated reconnection. Our model results show that for CA = 0∘, antiparallel reconnection at both the northern and southern lobes causes a reverse dispersion in which ion energies increase with increasing latitude. For CA = 60∘, unsteady antiparallel reconnection at both the northern and southern lobes causes double reverse dispersions. For CA = 120∘, component reconnection near the subsolar point produces a dispersionless signature in the low‐latitude cusp, and antiparallel reconnection on the duskside northern magnetopause produces a normal dispersion in the high‐latitude cusp in which ion energies decrease with increasing latitude. For CA = 180∘, antiparallel reconnection near the subsolar point causes a normal dispersion.