July 9, 2010, 12:00 pm - 1:00 pm

July 9, 2010, 12:00 pm - 1:00 pm

Evolution of magnetic flux ropes at Earth’s magnetopause

Hiroshi Hasegawa (ISAS)

Even after the advent of multi-spacecraft missions such as Cluster and THEMIS, it has been difficult to distinguish between time evolution of, and spatial variation within, a space plasma structure on the basis of in situ measurements. We present a method for analyzing time evolution of two-dimensional (2D), magnetohydrostatic equilibria, using data recorded by an observing probe as it traverses a quasi-static, 2D, magnetic-field/plasma structure. The method recovers spatial initial values used in the classical Grad-Shafranov (GS) reconstruction (Hau and Sonnerup, 1999) for an interval before and after the time of actual measurements, by advancing them backward and forward in time based on a set of equation for an incompressible plasma; the consequence is generation of multiple GS maps or a movie of the 2D field structure. The method is successfully benchmarked by use of a 2D magnetohydrodynamic simulation of time-dependent magnetic reconnection, and is applied to a magnetic flux transfer event (FTE) seen by the Cluster spacecraft at the dayside high-latitude magnetopause (Hasegawa et al., 2006). Possibilities of application to flux ropes in the magnetotail and magnetic clouds in the solar wind are also discussed.