Heliospheric tomography using interplanetary scintillation observations

Abstract

We have produced a Computer Assisted Tomography (CAT) program that optimizes a three dimensional solar wind velocity, V, and density fluctuation, ΔN e , model to fit observed interplanetary scintillation (IPS) data from Nagoya, Japan and Cambridge, England. The multiple perspective views of the solar wind needed for the reconstruction solution are provided by solar rotation and outward solar wind motion. The CAT program iterates to a least squares fit solution to the observed IPS values. We map the model to one AU and compare this to in situ observations from the IMP spacecraft. From this comparison we find ΔN e ∝ N 0.3 e . We plot the optimized model as Carrington maps in velocity and ΔN e , and compare these with Yohkoh Carrington synoptic maps. We find that the model velocity projected to the solar surface for individual rotations shows regions of high velocity that map directly to coronal hole areas observed in Yohkoh Soft X-ray Telescope (SXT) observations. Regions of slow velocity generally map to bright regions in SXT data. Regions of high ΔN e show a high correlation with regions of high solar activity observed as bright in Yohkoh SXT observations.