Reconstructed global feature of the interplanetary disturbance for the full-halo coronal mass ejection event on 1999 September 20

The full-halo coronal mass ejection (CME) occurred on September 20, 1999, in association with the C2.8 flare and the disappearing solar filament in the southern hemisphere, and an impact of this full-halo CME to the earth's magnetosphere resulted in an occurrence of the major geomagnetic storm during September 22--23. Traveling interplanetary (IP) disturbance caused by the full-halo CME was observed clearly from radio scintillation measurements taken on September 21--22, 1999, with the 327 MHz four-station system of the Solar-Terrestrial Environment Laboratory, Nagoya University. The IP disturbance showed a ring-shaped distribution encircling the sun in the sky projection map of our scintillation data. This feature is interpreted as a manifestation of an Earth-directed traveling disturbance with a thin radial extent, and it is consistent with the appearance of the full-halo CME. In the present study, we have deduced accurate (i.e. undistorted by the line-of-sight integration effect) information on the spatial distribution of the IP disturbance by fitting a three-dimensional model to our scintillation data. As result, we have obtained the best fit model, which has a bubble-like structure with a center axis shifted to the south with respect to the sun-earth line and a nearly isotropic angular span, for this IP disturbance event. The reconstructed global feature is found to be in good agreement with in situ measurements by ACE and Nozomi spacecraft, which are situated near the earth and distantly from the earth, respectively.