Automatic Identification of Magnetopause Crossing Events

The magnetopause is the key area of mass, momentum and energy coupling between the solar wind and the magnetosphere. The Magnetopause Crossing Events (MCEs) are usually identified by visual inspection of the plots, which is labor intensive and inefficient. Here we develop a novel procedure that is able to rapidly identify MCEs around the subsolar point and accurately define the transition layer between the magnetosphere and the magnetosheath. Here we synthetically consider the characteristics of the variations of the magnetic field and the particle flux for the identification criteria so that false identifications are avoided to the greatest possible. To demonstrate the efficiency of this procedure, it is applied to the THEMIS observations from 2007 to 2018 when THEMIS's apogee is near the subsolar point. The procedure successfully determines 16758MCEs in about 6 hours on a common PC. The huge number of identified samples of MCEs would benefit the investigations on the magnetopause-related scientific problems, such as indentation of the magnetopause, solar wind-magnetosphere interaction, magnetic reconnection process, and so on. The accuracy and limitation of this algorithm are also analyzed in this paper.