Evidence for pearl-like magnetic island structures at dawn and dusk side magnetopause

Two-dimensional magnetopause structure with a series of pearl-like magnetic islands at the dawn side of the equatorial plane was reported earlier by Hau and Sonnerup (1999) from the AMPTE/IRM data by solving the Grad-Shafranov equation as a spatial initial value problem. This paper presents another rare event that appears like the image of the dawn event at the dusk side magnetopause based on the analysis of two years satellite data and similar reconstruction method. The two crossings occur at (x, y, z) = (7.13,−6.64, 0.4) and (7.93, 9.06,−1.89)R ^E with magnetopause normal n̂ being (0.85,−0.52, 0.003) and (0.82, 0.55,−0.17) in the GSE coordinates, respectively. Both events are tangential discontinuity-like structures with shear angles being 124° and 97° and convect tailward with the deHoffmann-Teller frame velocity V^HT of (−141.88,−215.47,72.48) and (−100.26, 144.52,20.90) (km/s), respectively, that form approximately 90° from n̂. The magnetic field configurations in both cases show great similarity with the same island width of ∼500 km and aspect ratio of ∼0.2.