A Parametric Study of the Structure of Hall Magnetic Field Based on Kinetic Simulations. II. Asymmetric Magnetic Reconnection with a Guide Field

In this paper, with a two-dimensional (2D) particle-in-cell simulation model, we investigate the structure of Hall magnetic field generated in asymmetric magnetic reconnection with a guide field. It is found that the structure of the Hall magnetic field on the left side of the X line is different from that on the right side. In general, the Hall magnetic field on the left side has a tripolar structure, while it has a bipolar structure on the right side. On the left side of the X line, the Hall magnetic field at the upper and lower parts of the current sheet is positive, while that in the central part is negative. With the increasing guide field, the amplitude of the Hall magnetic field at the upper and center parts of the current sheet decreases, and that at the lower part increases. An increasing asymmetry (either an increase of the ratio of the magnetic field or decrease of the density ratio between the two sides of the current sheet, and the ratio is defined as the values between the side with the stronger magnetic field to that with the weaker magnetic field) leads to the decrease of the Hall magnetic field at the upper part of the current sheet and even disappearance when the asymmetry is sufficiently large, and the increase of the Hall magnetic field at the lower and central parts of the current sheet. On the right hand of the X line, the Hall magnetic field at the upper part of the current sheet is negative, while that at the central part is positive. With the increasing guide field, the Hall magnetic field at the upper current sheet increases, while that at the central current sheet decreases. The increasing asymmetry leads to the decrease of the Hall magnetic field at the upper and central parts of the current sheet, and when the asymmetry is sufficiently large there appears the Hall magnetic field below that at the central current sheet.