The UCSD Iterative Interplanetary Scintillation (IPS) Analysis Using an ENLIL 3-D MHD Model Kernel in Near Real Time

The University of California, San Diego has developed a time-dependent three-dimensional (3-D) reconstruction technique that provides volumetric maps of density and velocity by iteratively fitting 3-D MHD models to interplanetary scintillation (IPS) observations. We have applied a similar technique in near real time to the Institute for Space-Earth Environmental Research, Japan IPS data for nearly 20 years. However, unlike the previous UCSD kinematic modeling, our new tomographic analysis with a 3-D MHD kernel now includes shock processes and non-radial transport. Magnetic fields extrapolated outward from the solar surface, and in-situ spacecraft measurements near Earth are also included to support the iterative procedure. Tests of this analysis show that it constrains amplitude and radial extent better than the kinematic model for a system operated in near real time. This is especially important when more data are available from the Worldwide IPS Stations (WIPSS) network groups where both spatial and temporal coverage is increased. Cone model inputs to 3-D MHD modeling can also provide fast CME onsets sometimes missed initially by the IPS, as well as pin onsets to a specific time and solar surface location. Here we concentrate on the application of the ENLIL heliospheric 3-D MHD code as a kernel in the UCSD 3-D tomography, and show what is required to incorporate innovations such as cone model inputs into these new analyses.