The IMF dependence of the magnetopause from global MHD simulations

Abstract

[1] Numerical results from a physics-based global magnetohydrodynamic (MHD) model are used to investigate the controlling effects of the interplanetary magnetic field (IMF) components, B Y and B Z , on the location and shape of the magnetopause. The subsolar magnetopause is identified by using the plasma density and velocity, the cusp by using the current density, and the other area by streamlines and the current density. These data are fitted with a three-dimensional surface function constructed by Liu et al. (2012), which allows description of the cusp geometry as well as the north-south asymmetry and azimuthal asymmetry of the magnetopause. A new parameter which depends on the IMF B Y and B Z is introduced to describe the orientation of the elliptical cross section of the magnetopause. Effects of IMF B Y and B Z on the magnetopause configuration parameters are analyzed, and dependence of the magnetopause parameters in the IMF components are obtained. Magnetopause cross section is found to be largely controlled by the IMF clock angle. The stretch direction of the magnetopause cross section is always near the direction of the IMF but is a little closer to the meridional plane than the IMF. Increasing B Y or B Z increases the eccentricity of the magnetopause cross section. This effect is larger for southward IMF than for the northward IMF, and the stretching effect of B Y is smaller than that of B Z .

In situ magnetotail magnetic flux calculation

“…10. It is also worth noting that the same sign of the R T 0 (IMF B z ) dependence was obtained for the BATS-R-US "empirical" magnetopause model (Lu et al, 2013). This conformity with our new formula could be the main reason for the estimation improvement described in Sect.…”

The influence of IMF clock angle on the cross section of the tail bow shock

“…This model has been applied to study numerous aspects of the magnetospheric physics in the past [e.g., Song and Russell , ; Gombosi et al , ; Kabin et al , ; Zhang et al , ; Tóth et al , ] and is thoroughly validated [e.g., Welling and Ridley , ; Rae et al , ]. Recently, we have used the SWMF to study the global magnetopause shape and its dependence on the solar wind conditions [ Lu et al , , , ; Liu et al , , ], as well as the energy transfer across the magnetopause [ Lu et al , ; Jing et al , ]. This model was also used by Wang et al [] to analyze the influence of the dipole tilt angle on the shape and size of the bow shock.…”

“…For example, Nakamura et al [] reported that during quiet intervals when IMF B y exceeds B z the dawn‐dusk extent in the distant magnetotail exceeds its north‐south extent, but during the main and recovery phases of geomagnetic storms when IMF B z exceeds B y the reverse is true. Detailed study of Lu et al [] based on global modeling of the magnetosphere showed that magnetopause cross section is elongated in the direction fairly close to that of the IMF. Observations discussed by Lavraud et al [] confirmed this and also showed that this asymmetry is more pronounced in the case of low Mach numbers.…”

Effects of the interplanetary magnetic field on the twisting of the magnetotail: Global MHD results

“…Hasegawa et al [2002aHasegawa et al [ , 2002b studied IMF dependence of the distant tail shape using the plasma and magnetic field measurement and found that the yz cross section of magnetotail stretches along IMF direction. Recently, using the MHD simulations, Lu et al [2013] improved the three-dimensional model on the basis of Liu et al [2012] to investigate the influence of IMF B y and B z on the shape of magnetopause. They found that the stretch direction of the magnetopause cross section is always near the direction of the IMF but is a little closer to the meridional plane than the IMF.…”