Global MHD simulation of flux transfer events at the high‐latitude magnetopause observed by the Cluster spacecraft and the SuperDARN radar system

Abstract

[1] A global magnetohydrodynamic numerical simulation is used to study the large-scale structure and formation location of flux transfer events (FTEs) in synergy with in situ spacecraft and ground-based observations. During the main period of interest on the 14 February 2001 from 0930 to 1100 UT the Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the postnoon sector on an outbound trajectory. Throughout this period the magnetic field, electron, and ion sensors on board Cluster observed characteristic signatures of FTEs. A few minutes delayed to these observations the Super Dual Auroral Radar Network (SuperDARN) system indicated flow disturbances in the conjugate ionospheres. These ''two-point'' observations on the ground and in space were closely correlated and were caused by ongoing unsteady reconnection in the vicinity of the spacecraft. The three-dimensional structures and dynamics of the observed FTEs and the associated reconnection sites are studied by using the BlockAdaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) MHD code in combination with a simple open flux tube motion model (Cooling). Using these two models the spatial and temporal evolution of the FTEs is estimated. The models fill the gaps left by measurements and allow a ''point-to-point'' mapping between the instruments in order to investigate the global structure of the phenomenon. The modeled results presented are in good correlation with previous theoretical and observational studies addressing individual features of FTEs.

Magnetic Reconnection at a Thin Current Sheet Separating Two Interlaced Flux Tubes at the Earth's Magnetopause

“…A mixture of magnetosheath and magnetospheric ion and electron populations is often detected within FTEs (Le et al, ). FTEs have been studied using simulations (Daum et al, ; Fedder et al, ; Raeder, ), laboratory experiments (e.g., Egedal et al, ; Fox et al, ; Stenzel & Gekelman, ; Yamada, ), ground measurements (Lockwood, Fazakerley, et al, ; Lockwood, Opgenoorth, et al, ; Wild et al, ), and multispacecraft missions as Cluster (e.g., Fear et al, ; Hasegawa et al, ; Roux et al, ; Sönnerup et al, ), Time History of Events and Macroscale Interactions during Substorms (Fear et al, ; Silveira et al, ), and now MMS (Farrugia et al, ; Hwang et al, ). FTE models can essentially be classified into three types of models: elbow‐shaped flux rope model (Russell & Elphic, ), multiple X‐line model (Lee & Fu, ), and single X‐line model (Fear et al, ; Scholer, ; Southwood et al, ).…”

Joint Cluster/Ground‐Based Studies in the First 20 Years of the Cluster Mission

“…Daum et al. (2008), reinvestigating the conjunction (discussed above) analyzed by Wild et al. (2001, 2003), took the qualitative comparison of Q.‐H.…”

“…Several studies (Daum et al, 2008;Q.-H. Zhang et al, 2008Q.-H. Zhang et al, , 2010 have sought to compare the propagation of reconnected flux tubes as observed simultaneously at the magnetopause (in the form of FTE signatures observed by Cluster) and in the ionosphere (as PIFs/PMAFs observed by optical instrumentation or radars). Q.-H. Zhang et al (2008) found qualitative agreement between the northward and dawnward motion of the FTEs observed by Cluster (consistent with the motion predicted by the Cooling et al (2001) model) and the northward and westward flow observed by SuperDARN at the conjugate point in the northern hemisphere ionosphere.…”

Introduction to special section on Double Star‐Cluster Coordinated Studies on Magnetospheric Dynamic Processes

“…The FTE was moving at a fraction of the magnetosheath flow and producing a traveling magnetopause erosion region in its wake. Daum et al [2008] modeled an FTE event observed by ground‐based SuperDARN radars and Cluster using MHD simulation combined with a model of flux tube motion (cooling). They could estimate the spatial and temporal evolution of the FTE.…”