Magnetopause reconnection across wide local time

Abstract

Abstract. During April to July 2007 a combination of 10 spacecraft provided simultaneous monitoring of the dayside magnetopause across a wide range of local times. The array of four Cluster spacecraft, separated at large distances (10 000 km), were traversing the dawn-side magnetopause at high and low latitudes; the five THEMIS spacecraft were often in a 4 + 1 grouped configuration, traversing the low latitude, dusk-side magnetosphere, and the Double star, TC-1 spacecraft was in an equatorial orbit between the local times of the THEMIS and Cluster orbits. We show here a number of near simultaneous conjunctions of all 10 spacecraft at the magnetopause. One conjunction identifies an extended magnetic reconnection X-line, tilted in the low latitude, sub-solar region, which exists together with active anti-parallel reconnection sites extending to locations on the dawn-side flank. Oppositely moving FTE's are observed on all spacecraft, consistent with the initially strong IMF B y conditions and the comparative locations of the spacecraft both dusk-ward and dawn-ward of noon. Comparison with other conjunctions of magnetopause crossings, which are also distributed Correspondence to: M. W. Dunlop (m.w.dunlop@rl.ac.uk) over wide local times, supports the result that reconnection activity may occur at many sites simultaneously across the sub-solar and flank magnetopause, but linked to the large scale (extended) configuration of the merging line; broadly depending on IMF orientation. The occurrence of MR therefore inherently follows a "component" driven scenario irrespective of the guide field conditions. Some conjunctions allow the global magnetopause response to IMF changes to be observed and the distribution of spacecraft can directly confirm its shape, motion and deformation at local noon, dawn and dusk-side, simultaneously.

Magnetospheric Multiscale Science Mission Profile and Operations

“…The location of reconnection is empirically related to regions of high and intermediate shear. The empirical model has been validated in several independent tests Dunlop et al 2011;Trattner et al 2012). The model predicts the location of the reconnection line using the interplanetary magnetic field (IMF) orientation.…”

The MMS Dayside Magnetic Reconnection Locations During Phase 1 and Their Relation to the Predictions of the Maximum Magnetic Shear Model

“…This model suggests that magnetopause reconnection occurs where the magnetic shear angle between the magnetospheric and draped magnetosheath magnetic fields is a maximum. It has been used in many studies involving observations from various satellites (Polar, Cluster, THEMIS, IBEX, Cassini) (Dunlop et al, ; Fuselier et al, , ; Petrinec et al, ; Trattner et al, , ; Vines et al, ) and magnetohydrodynamic (MHD) simulations (Komar et al, ) and was successfully validated. The maximum magnetic shear model was also used during the MMS design effort to optimize and predict the number of reconnection location encounters for the dayside phases 1a and 1b (Fuselier et al, ).…”

Inner plasma structure of the low‐latitude reconnection layer

“…These boundaries (‘P’, ‘Q’, ‘R’, and ‘S’) are identified by the sharp boundaries in the electron anisotropy data (Figure 4i) and in the FBK electric field spectrum data (Figure 4j). During the interval of interest, the IMF clock angle varied between −90 and −60°, which is believed to be favorable for the occurrence of lobe reconnection poleward of the cusp region and simultaneous low‐latitude reconnection at the flank magnetopause [ Lockwood and Moen , 1999; Pu et al , 2007; Trattner et al , 2007; Dunlop et al , 2011]. Noting that the magnetosheath clock angle observed by TH‐B sometimes disagreed with the IMF clock angle as TH‐B sometimes went to the boundary layer.…”