Magnetosheath reconnection before magnetopause reconnection driven by interplanetary tangential discontinuity: A three-dimensional global hybrid simulation with oblique interplanetary magnetic field

Terrestrial dayside dynamics associated with a southward turning interplanetary magnetic field (IMF) carried by an interplanetary tangential discontinuity (TD) is investigated by performing a three-dimensional (3D) global-scale hybrid simulation. Magnetosheath reconnection is found downstream of the bow shock due to interaction of the directional TD with the bow shock and magnetopause. Results of several runs are presented, in which the unperturbed IMF is in the GSE  plane, with a cone angle of 150 degree . The incoming solar wind TD possesses various magnetic field rotation angles  to  and half-widths. Overall, the TD is compressed while being transmitted into the magnetosheath, with different compression processes downstream of the Q-|| and Q-  shocks. Various magnetosheath flux ropes are formed through 3D patchy reconnection in the thinned current sheet. When rotation angle decreases to 90 degree, no reconnection flux ropes are found. Magnetopause reconnection is initiated when a southward turning IMF reach the magnetopause, and the magnetopause flux ropes can be mixed with the magnetosheath ones. Our simulation demonstrates that the effects of a southward turning of the IMF may not be a simple field direction change that leads to reconnection only at the magnetopause.