Dual-Spacecraft Reconstruction of a Three-Dimensional Magnetic Flux Rope at Earth's Magnetopause

Abstract:

We present first results of a data analysis method, developed by Sonnerup and Hasegawa (2011), for reconstructing three-dimensional (3-D), magnetohydrostatic structures from data taken as two closely spaced satellites traverse the structures. The method is applied to a flux transfer event (FTE), which was encountered on 27 June 2007 by at least three (TH-C, TH-D, and TH-E) of the five THEMIS probes and was situated between two oppositely directed reconnection jets near the subsolar magnetopause under a southward interplanetary magnetic field condition. The recovered 3-D field indicates that a magnetic flux rope with a diameter of ~3000 km was embedded in the magnetopause. The FTE flux rope had a significantly 3-D structure, because the 3-D field reconstructed from the data from TH-C and TH-D (separated by ~390 km) better predicts magnetic field variations actually measured along the TH-E path than 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 ~1000 km from TH-E). Such a 3-D nature suggests that reconnected field lines from the two reconnection sites are entangled in a complicated way through their interaction with each other. The generation process of the observed 3-D flux rope is discussed on the basis of the reconstruction results and the pitch-angle distribution of electrons observed in and around the FTE.

Reference:

Sonnerup, B. U. Ö., and H. Hasegawa (2011), Reconstruction of steady, three-dimensional, magnetohydrostatic field and plasma structures in space: Theory and benchmarking, J. Geophys. Res., 116, A09230, doi:10.1029/2011JA016675.