Three‐dimensional hybrid simulation of magnetosheath reconnection under northward and southward interplanetary magnetic field

Abstract

[1] A three-dimensional (3-D) global hybrid simulation is carried out for the generation and structure of magnetic reconnection in the magnetosheath because of the interaction of an interplanetary tangential discontinuity (TD) with the bow shock and magnetosphere. Runs are performed for solar wind TDs possessing different polarization senses of magnetic field (north-to-south or south-to-north from the leading to trailing side of the incident TD) and initial half-widths. Two-step compression processes are shown in the transmitted TD, including a "shock compression," as the TD passes through the shock followed by a subsequent "convective compression" while the TD is moving in the magnetosheath toward the magnetopause. In cases with a relatively thin solar wind TD, 3-D patchy reconnection is initiated in the transmitted TD, forming magnetosheath flux ropes. Differences between these flux ropes and those due to magnetopause reconnection are discussed. Multiple components of ion particles are present in the velocity distribution in the magnetosheath merging, accompanied by ion heating. For cases with a relatively wide initial TD, a dominant single X line appears in the subsolar magnetosheath after the transmitted TD is narrowed through the two-step compression process. Specifically, in the cases with a south-to-north field rotation across an incident thin TD, the magnetosheath flux ropes could re-reconnect with the closed geomagnetic field lines to generate a closed field line region with mixed magnetosheath and magnetospheric plasmas, which may contribute to the transport of solar wind plasma into the magnetospheric boundary layer.

Triggering of magnetic reconnection in a magnetosheath current sheet due to compression against the magnetopause

“…Both of these changes are favorable for the onset of reconnection. The observations thus suggest that reconnection was initiated near the magnetopause as the result of strong compression of the magnetosheath current sheet against the low-shear magnetopause, in agreement with the simulation results of Pang et al [2010].…”

“…However, it could not be determined in that study whether it was the compression across the bow shock or the compression against the magnetopause that was more significant for triggering reconnection. Recent 2D and 3D global hybrid simulations suggest that while the bow shock does compress solar wind TDs, compression across the bow shock alone would be insufficient to initiate reconnection in originally thick solar wind TDs and additional compression against the magnetopause would be required [Omidi et al, 2009;Pang et al, 2010].…”

Magnetosheath Reconnection Before Magnetopause Reconnection Driven by Interplanetary Tangential Discontinuity: A Three‐Dimensional Global Hybrid Simulation With Oblique Interplanetary Magnetic Field

“…Using Cluster spacecraft observations, Phan et al (, ) and Hasegawa et al () have identified the initiation of magnetosheath reconnection due to compression of a solar wind current sheet at the bow shock and against the dayside magnetopause. The observation event of Phan et al () has been simulated by performing a two‐dimensional (2‐D; Omidi et al, ) and a three‐dimensional (3‐D) global hybrid simulation (Pang et al, ) for the generation and structure of magnetosheath reconnection due to the interaction between an interplanetary TD and the Q‐⊥ bow shock.…”

Jets Downstream of Collisionless Shocks

“…Using Cluster data these authors showed that thin current sheets with typical scales of a few ion inertial lengths (∼100 km) are found downstream of the quasi-parallel shock, and that reconnection can occur at them. Furthermore, observations reported by Phan et al (2007) and simulations by Pang et al (2010) have given evidence that reconnection jets can occur in the magnetosheath due to the compression of solar wind current sheets at the bow shock. More work is needed, however, to determine if reconnection at these sheets can be related to the magnetosheath jets discussed herein.…”