Large-scale solar-wind structure near the Sun detected by Doppler scintillation

摘要: STUDIES of the solar wind in inner heliosphere (between solar-wind source surface at ∼0.01 AU and 0.3 AU) are hampered by lack situ spacecraft measurements. Radio propagation measurements—using both natural1–7 spacecraft8–14 radio signals—have provided many insights, but information on large-scale structure inside that can be related to coronal features or direct measurements larger distances has nevertheless remained elusive. Here we report detection between 0.08 0.53 AU, based response 13-cm signals from Pioneer Venus Orbiter electron-density fluctuations speed within this region. These Doppler scintillation were made during late declining phase most recent cycle activity, when exhibited recurrent high-speed streams. Near 0.5 find narrow regions enhanced which appear associated with compressed plasma leading edges these streams, consistent previous measurements15,16. Inside 0.2 however, enhancements conspicuously absent fast instead occur where average is slow. They exhibit high variability, interplanetary manifestation mass ejections. The structures giving rise scintillations apparently undergo significant evolution AU.