The Distribution of Two Flapping Types of Magnetotail Current Sheet: Implication for the Flapping Mechanism

Abstract Flapping motion of the current sheets of planetary magnetotails is a common dynamic phenomenon. Previous studies of the Earth's magnetotail suggest that its flapping motion has two forms, that is, kink‐like flapping that can propagate as waves toward both flanks and steady flapping that moves up and down but does not propagate. Although some models have been proposed to explain the kink‐like flapping, its mechanism remains unclear. This paper surveys 87 flapping events statistically with respect to their flapping types, using the multipoint measurements of Cluster. The statistical results show that the up‐down steady flapping events tend to occur around the midnight region, and the kink‐like flapping events tend to occur near both flanks of the magnetotail. Thus, we propose that kink‐like flapping motion is causally related to steady flapping motion; that is, the up and down motion of steady flapping around the midnight region induces kink‐like flapping waves, which propagate toward both flanks of the magnetotail.