Analysis of magnetotail flux rope events by ARTEMIS observations

Three earthward flowing magnetic flux ropes observed in the duskside plasma sheet at geocentric solar magnetospheric coordinate X ～?55 Re by P1 and P2 of acceleration, reconnection, turbulence and electrodynamics of moon’s interaction with the sun mission during 13:00–15:00 UT on July 3, 2012, were studied. The morphologies of the flux ropes were studied in detail based on Grad-Shfranov reconstruction method and electronic pitch angle distribution data. It is found that (1) the flux rope cross-sectional dimensions are 1.0 Re× 0.78 Re, 1.3 Re×0.78 Re, and 2.5 Re × 1.25 Re, respectively. The magnetic field lines were asymmetric about the center with field line compression on both sides of the current sheet at the leading region; (2) the electron energy flux data presented asymmetry with larger electron flux and lower temperature in the precursor region. The flux ropes were blocked by the resistance of compressed particle density in the front central plasma sheet and the enhanced magnetic field on its sides; and (3) it is found that the flux rope has a layered structure. From inside out, event 1 can be divided into three regions, namely electronic depletion core region, closed field line region, and the caudal area possible with fields connected with the ionosphere. It suggests that the flux ropes cannot merge with the tail magnetic field lines near the lunar orbit. Especially, the flux rope asymmetrical shape reflects the different reconnection processes that caused it on both sides of the magnetic structure. The events shown in this paper support the multiple X-line magnetic reconnection model for flux ropes with in situ observations.