IWIDENCIC FOR Hill RWERSAI. OIJ MAGNETIC FIIHJ) POI,AIUTY IN CORONA1, STREAMERS

Faraclay rotation observations are unique amongst radio occultation mcasurcmcnts in that they respond to magnetic field in addition to e.lcctron density, making it possible to probe the coronal magnetic field. Transients observed by Pioneer 6 Faraday rotation measurements in 1968 in the heliocentric distance range of 6-11 R. arc shown to be caused by the radially expanding coronal streamer stalks of angular size 1-2° observed in whitclight measurements rather than the magnetic bottles interpreted earlier. This identification makes available the first magnetic field observations of coronal streamers. The detection of the reversal of magnetic field polarity high in the corona provides observational evidence confirming what has previously only been inferred from modeling — that streamers observed in white-light measurements are the maniftxtation of the hcliospheric current sheet. These results reinforce the apparent connection between the coronal streamer stalks and the plasma sheets in the solar wind identified by in situ fields and particles measurements beyond 0.3 AU. Introduction Radio occultation measurements using natural radio sources and spacecraft radio signals have probed the solar corona for many years [Hewish 1972, Bird and Edenhofcr 1990, Coles 1993, Woo 1994, 1996a]. Based on a wide variety of radio propagation and scattering phenomena, these measurements include angular broadening, intensity scintillation, ranging, and others. Decades of observation have produced considerable information on electron density and its fluctuation, as well as solar wind velocity. }~araday rotation of a linearly polarized radio wave is uniclue amongst radio occultation