DOPPLER SCINTILLATION MEASUREMENTS OF THE HELIOSPHERIC CURRENT SHEET AND CORONAL STREAMERS CLOSE TO THE SUN

Prominent enhancements in Doppler scintillation lasting a fraction of a day (solar source several degrees wide) and overlying the neutral li ne represent the signature of the heliospheric current sheet and the a pparent interplanetary manifestation of coronal streamers near the Sun . This first detection of coronal streamers in radio scintillation mea surements provides the link between in situ measurements of the spatia l wavenumber spectrum of electron density fluctuations beyond 0.3 AU a nd earlier measurements deduced from radio scintillation and scatterin g observations inside 0.3 AU. Significant differences between the dens ity spectra of fast streams and slow solar wind associated with the he liospheric current sheet near the Sun reinforce the emerging picture t hat high- and low-speed flows are organized by the large-scale solar m agnetic field, and that while the contrast between solar wind properti es of the two flows is highest near the Sun, it undergoes substantial erosion in the ecliptic plane as the solar wind expands.