Heliospheric tomography using interplanetary scintillation observations: 1. Combined Nagoya and Cambridge data

Abstract

We have produced a computer assisted tomography program that optimizes a three‐dimensional model to fit observational data. We have used this program with interplanetary scintillation data from Nagoya, Japan, and Cambridge, England. The program iterates to a least squares solution fit of observed data using solar rotation and solar wind motion to provide perspective views of each point in space accessible to the observations. We plot the optimized model as Carrington maps in velocity V and density Ne for the two data sets with resolutions of 10° in heliographic longitude and latitude. We map the model to 1 AU and compare this to in situ observations from the IMP spacecraft. From this comparison we find ΔNe ∝ Ne0.3. We plot Carrington maps extrapolated to the solar surface to compare with Yohkoh Soft X ray Telescope (SXT), Sacramento Peak green line, and Mark III K‐coronameter observations. High velocities modeled at the solar surface for individual rotations trace coronal holes (including polar ones) observed in SXT data. Regions of high density modeled from the Cambridge scintillation level data generally show a high correlation with regions of high solar activity observed as bright in Yohkoh SXT and green line observations. There is also a general correspondence of the regions of high density and the areas which are bright in K‐coronameter observations.