Radio-sounding observations of a coronal mass ejection during the Galileo solar conjunction in January 1997

Abstract

Frequency and amplitude fluctuations of the Galileo S-band radio signal were recorded nearly continuously during the spacecraft's solar conjunction from December 1996 to February 1997. A strong propagating disturbance associated with a CME was detected on 8 January when the radio ray path proximate point was on the east solar limb at about 32 solar radii from the Sun. Characteristics of the CME passage through the Galileo/Earth line of sight include: (a) a noticeable change of the average frequency of the radio signal, (b) a significant increase in the fluctuation level of the radio frequency and amplitude, and (c) a dual-velocity solar wind configuration with distinctly different values of the velocity (200 km/s and 360 km/s). These velocity estimates are obtained from a correlation analysis of frequency fluctuations recorded simultaneously at two widely-separated ground stations. The frequency fluctuation cross-correlation functions are relatively narrow during the passage of the disturbance through the...