Background Coronal mass ejections of the 1997 (January, February, May)

OBSERVATION OF THE JANUARY 1997 CORONAL MASS EJECTION NEAR

THE SUN USING RADIO SOUNDING TECHNIQUE WITH GALILEO

SPACECRAFT

A.I. Efimov, L.N. Samoznaev, V.K. Rudash, I.V. Chashei,M.K. Bird, D. Plettemeier

Inst. Radio Eng. Electr., Russian Acad. Sci., 125009 Moscow, RussiaLebedev Phys. Inst., Russian Acad. Sciences, 117924 Moscow, Russia

Radioastronomisches Institut, Univ. Bonn, 53121 Bonn, GermanyTechnische Univ.Dresden,Electrotech.Inst., 01062 Dresden, Germany

Background

Coronal mass ejections of the 1997 (January, February, May) extensively were studied using in situ methods and remote-sensing technique, based on the analysis of the type II radio emissions, generated by CME [Fox et al, 1998].

Other remote-sensing technique based on radio sounding of the solar wind by the signals of spacecraft provides a valuable information about CME properties in the intermediate heliocentric distance range between the solar corona and Earth.

During the GALILEO January 1997 ingress S-band signal data were acquired when the radio ray path proximate point was on the east limb at distances 34…28 solar radii from the Sun.

GALILEO-97: Frequency Residual at Three Ground Stations

(a) GALILEO-97 DOY 8-11, S-band Average Frequency Residuals; (b) WIND-97 (DOY 8-11), Electron Density

GALILEO-97: Intensity of Frequency Fluctuations

GALILEO-97: Spectral Index of Frequency Fluctuation

GALILEO-97: Cross-Correlation Functions of Frequency Fluctuations

Conclusions

1. The GALILEO Solar Conjunction in January 1997 showed the high sensitivity of the sounding signals to the disturbed plasma formations.

2. The passage of coronal mass ejections through radio ray path causes the next radio effects:

- strong (2-3 fold) increase of the frequency fluctuations;

- a steeping of temporal spectra during passage of the leading front of CME;

- blue shift of the average frequency at passage of the leading front and red shift at passage of the trailing part of CME;

- cross-correlation functions of the frequency fluctuations with the two maxima.