AbstractMeasurements of solar wind velocity have been derived from simultaneous coronal sounding observations of radio amplitude scintillations at both S-band and X-band during the solar conjunction of the Ulysses spacecraft in August 1991. The signal amplitude was recorded with an averaging time of 1s. A cross-correlation analysis between S- and X-band amplitude fluctuations shows that the fluctuation signature at S-band appears to be shifted to earlier times with respect to the X-band recording. The time difference is proportional to the coronal separation of the ray paths and inversely proportional to the apparent velocity of plasma inhomogeneities across the ray paths. Preliminary estimates of solar wind speed obtained using model calculations of the differential refraction are found to lie near the expected transition from subsonic to supersonic velocities at solar offset distances of the order of 6–8R⊙. As a byproduct of the investigation, we find that the transition from weak to saturated scintillation occurs at about 16R⊙ for S-band and 7R⊙ for X-band.


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    Title :

    Solar wind velocity measurements near the sun using Ulysses radio amplitude correlations at two frequencies


    Contributors:
    Efimov, A.I. (author) / Bird, M.K. (author) / Rudash, V.K. (author) / Andreev, V.E. (author) / Chashei, I.V. (author) / Plettemeier, D. (author) / Edenhofer, P. (author)

    Published in:

    Advances in Space Research ; 35 , 12 ; 2189-2194


    Publication date :

    2004-12-04


    Size :

    6 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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