Dual-spacecraft reconstruction of a three-dimensional magnetic flux rope at the Earth's magnetopause

摘要

We present the first results of a data analysis method, developed by Sonnerupand Hasegawa (2011), for reconstructing three-dimensional (3-D),magnetohydrostatic structures from data taken as two closely spacedsatellites traverse the structures. The method is applied to a magnetic fluxtransfer event (FTE), which was encountered on 27 June 2007 by at leastthree (TH-C, TH-D, and TH-E) of the five THEMIS probes near the subsolarmagnetopause. The FTE was sandwiched between two oppositely directedreconnection jets under a southward interplanetary magnetic field condition,consistent with its generation by multiple X-line reconnection. Therecovered 3-D field indicates that a magnetic flux rope with a diameter of~ 3000 km was embedded in the magnetopause. The FTE flux ropehad a significant 3-D structure, because the 3-D field reconstructed fromthe data from TH-C and TH-D (separated by ~ 390 km) betterpredicts magnetic field variations actually measured along the TH-E paththan does the 2-D Grad–Shafranov reconstruction using the data from TH-C(which was closer to TH-E than TH-D and was at ~ 1250 km fromTH-E). Such a 3-D nature suggests that the field lines reconnected at thetwo X-lines on both sides of the flux rope are entangled in a complicatedway through their interaction with each other. The generation process of theobserved 3-D flux rope is discussed on the basis of the reconstructionresults and the pitch-angle distribution of electrons observed in and aroundthe FTE.