Comparison of the extent and mass of CME events in the interplanetary medium using IPS and SMEI Thomson scattering observations

Abstract

The Solar-Terrestrial Environment Laboratory (STELab), Japan, interplanetary scintillation (IPS) g-level and velocity measurements can be used to give the extent of CME disturbances in the interplanetary medium arising from the scattering of the radio waves from distant point-like natural sources through the intervening medium. In addition, white-light Thomson-scattering observations from the Solar Mass Ejection Imager (SMEI) have recorded the inner heliospheric response to several hundred CMEs. The work described here compares and details the difference in three-dimensional (3D) reconstructions for these two data sets for the well-observed 28 October 2003 halo CME seen in LASCO; this passed Earth on 29 October in the SMEI data at the same elongations as IPS g-level observations. The SMEI data analysis employs a 3D tomographic reconstruction technique that obtains perspective views from outward-flowing solar wind as observed from Earth, iteratively fitting a kinematic solar wind density model, and when available, including IPS velocity data. This technique improves the separation of the heliospheric response in SMEI from other sources of background noise, and also provides the 3D structure of the CME and its mass. The analysis shows and tracks outward the northward portion of a loop structure of this halo CME. We determine an excess mass for this structure of 6.7×10¹⁶ g and a total mass of 8.3×10¹⁶g in the SMEI analysis, and these are comparable to values obtained using IPS g-level data and a 3D reconstruction technique developed for these data and applied to this event. We also extend further the application for these analyses.

Keywords:

• Thomson scattering
• Interplanetary scintillation
• Computer assisted tomography
• Solar wind

Acknowledgements

B.V. Jackson and the group at UCSD acknowledge NSF grant ATM-0331513, NASA grants NAG5-13453 and NAG5-11906, and AFOSR grant FA9550-06-1-0107, to the University of California at San Diego for work on these analyses. We thank UCSD student John Clover for his participation in this project.