The distributions of the magnetic field fluctuation characteristics near the ecliptic plane in the magnetosheath are discussed by using the MHDmodel for describing variations of the interplanetary magnetic field fluctuations across a shock wave. The main results are: (1) the fluctuation intensity and fluctuation anisotropy of the interplanetary magnetic field are amplified obviously in the magnetosheath region; (2) when the interplanetary magnetic field is in the ecliptic plane, the magnetic field fluctuation characteristics (intersity, relative fluctuation and anisotropy and so on) show a dawn-dusk asymmetry, namely, the dawn-side (quasi-parallel shock wave) is more remarkable than the dusk-side (quasi-perpendicular shock wave) obviously; (3) the distribution characteristics are controled strongly by the directions of the interplanetary magnetic field, the dawn-side more sensitive than the dusk-side, relatively speaking, the magnetic activity of the dusk-side is more stable than the dawn-side; (4) the turn-southward of the interplanetary magnetic field will results the maximum fluctuation region moving from the ecliptic plane to the north pole-high latitude region, so that the south-north anisotropy of the magnetic activity will increase, which will reach a maximum when the angle between the interplanetary magnetic field and the ecliptic plane equals about 45°; (5) the dawn-dusk anisotropy will decrease with the increase of the relative fluctuation of the magnetic field.The distribution characteristics of the magnetic field fluctuations in the magnetosheath, obtained from our model, are consistent with the satellites observations and are the possible cause of some of the dawn-dusk asymmetry of the magnetopause and the boundary.
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