Empirical Reconstruction

Abstract

Empirical reconstruction methods attempt to interpret in situ observations of the magnetospheric boundary in terms of time-stationary structures that are convected past the spacecraft. The ever-changing position of the boundary is considered an unknown of the problem. Once the motion of the boundary is found, empirical reconstruction produces spatial maps showing how physical quantities vary as a function of position relative to the boundary. For a planar boundary moving at a constant speed, for instance, the time scale can be linearly transformed into a distance scale. While useful for short-duration magnetopause crossings (up to tens of seconds), a more powerful way of establishing boundary motion over a long time interval (hours, a whole boundary pass) is needed. A pioneering technique was proposed by Paschmann et al. [1990]. More advanced techniques have been developed since then. This chapter presents a generalised description of these methods and discusses their application.