Structure and dynamics of the plasma tail of comet P/Halley

Summary

An outstanding DE-like kink event occurred in the plasma tail of comet P/Halley on January 10–11, 1986. The kink was traced for 33 h in these days by surveying 24 photographs of the comet. The images of the kink on eleven representative photographs out of the 24 were transcribed on the Palomar Sky Survey Atlas to investigate its motion and formation. In order to explain the kink event, the following two problems are discussed: one is how the observed relation of the nucleus-kink distance, X, versus time, t, is explained, while the other is how the kink is formed. As for the observed X-t relation, a theoretical function, t=ʃcosh(X/X ₀)/[V ₀{cosh(X/X ₀)-1}+V _T]dX, is applied being based on the J×B acceleration process, where X ₀, V ₀, and V_T are characteristic length, final solar wind velocity, and initial (thermal) velocity, respectively. The expected curve coincides very well with the observation. As for the mechanism of the kink formation, an intrusion of an intermediate-velocity flow into a low-velocity flow along the tail axis is presented to be responsible taking into account a result of MHD computer simulation.