Dual spacecraft verification of magnetopause orientation and motion: Preliminary results

We attempt to validate results from multi-instrument, single spacecraft, methods for the determination of magnetopause speed and orientation from position and timing information, obtained through use of high time resolution, dual-spacecraft magnetic field data. The methods based on single spacecraft data rely on certain assumptions, whose validity can be tested, concerning boundary structure and stationarity, and therefore can differ in result. They determine most closely the local properties sampled by a particular spacecraft. The results of such analysis can be verified by comparison with timings of boundary crossings between two or more closely separated spacecraft. We undertake such validation using a range of crossings taken from the AMPTE UKS/IRM data set, which exhibit different boundary characteristics and occur for different spacecraft configurations with respect to the boundary. Our results indicate that, under favourable conditions, the single spacecraft methods yield magnetopause velocities that agree well with those derived from dual-spacecraft time shifts.