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Statistical study of the magnetopause motion: First results from THEMIS

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Abstract

[1] During its early coast phase the configuration of the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft resembled pearls on a string. Between April and September 2007 they traversed the magnetopause boundary layer far more than 6000 times. The radial extension of the spacecraft configuration as well as the resolution due to the high number of simultaneous observation points along the orbit provided us with the unique opportunity to study the spatiotemporal evolution of the magnetopause location. In this study we present single and multiple spacecraft analyses with a special emphasis on a statistical analysis of the magnetopause motion reconstructed from crossing locations and times by spline interpolation. Our observations allow us to infer a higher stability of the magnetopause surface against deformation in field-aligned direction. Its overall stability increases with decreasing distance to the Earth as well. Additionally, we were able to determine amplitude, velocity and period distributions of the boundary oscillations.

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