Three-dimensional reconstruction of heliospheric structure using iterative tomography: A review

Current perspective and in-situ analyses using data from NASA’s twin Solar TErrestrial RElations Observatory (STEREO) spacecraft have focused studies on ways to provide three-dimensional (3-D) reconstructions of coronal and heliospheric structure. Data from STEREO are proceeded by and contemporaneous with many other types of data and analysis techniques; most of the latter have provided 3-D information by relying on remote-sensing information beyond those of the near corona (outside 10 RS). These include combinations of past data from the Helios spacecraft and the Solwind coronagraphs and, continuing from the past to the present, from observations of interplanetary scintillation (IPS) and the Solar Mass Ejection Imager (SMEI) instrument. In this article we review past and ongoing analyses that have led to a current great wealth of 3-D information. When properly utilized, these analyses can provide not only shapes of CME/ICMEs but also a characterization of any solar wind structure or global outflow.