Coronal Mass Ejection Reconstructions from Interplanetary Scintillation Data Using a Kinematic Model: A Brief Review

Interplanetary scintillation (IPS) observations of multiple sources provide a view of the solar wind at all heliographic latitudes from around 1 AU down to coronagraph fields of view. These are used to study the evolution of the solar wind and solar transients out into interplanetary space, and also the inner-heliospheric response to co-rotating solar structures and coronal mass ejections (CMEs). With colleagues at the Solar Terrestrial Environment Labo- ratory (STELab), Nagoya University, Japan, we have developed near-real-time access of STELab IPS data for use in space-weather forecasting. We use a three- dimensional (3D) reconstruction technique that obtains perspective views of solar co-rotating plasma and of outward-flowing solar wind crossing our lines of sight from the Earth to the radio sources. This is accomplished by iteratively fitting a kinematic solar wind model to the IPS observations. This 3D modelling technique permits reconstructions of the density and speed structures of CMEs and other interplanetary transients at a relatively coarse resolution. These reconstructions have a 28-day solar-rotation cadence with 10° latitudinal and longitudinal heliographic resolution for a co-rotational model, and a one-day cadence and 20° latitudinal and longitudinal heliographic resolution for a time-dependent model. These resolutions are restricted by the numbers of lines of sight available for the reconstructions. When Solar Mass Ejection Imager (SMEI) Thomson-scattered brightness measurements are used, lines of sight are much greater in number so that density reconstructions can be better resolved. Higher resolutions are also possible when these analyses are applied to Ootacamund IPS data.