Visibility of Type III burst source location as inferred fromstereoscopic space observations

[摘要] We study solar Type III radio bursts simultaneously observed byRPWS/Cassini, URAP/Ulysses and WAVES/Wind experiments. Theobservations allows us to cover a large frequency bandwidthfrom 16 MHz down to a few kHz. We considerthe onset time of each burst, and estimate the correspondingintensity level. Also we measure the Langmuir frequency as observedon the dynamic spectra recorded by the Ulysses spacecraft. Thedistances of Wind, Ulysses and Cassini spacecraft, with regard tothe Sun, were in the order of 1 AU, 2.4 AU and 4.5 AU, respectively.The spacecraft trajectories were localized in the ecliptic planein the case of Wind and Cassini, and for Ulysses in the southernhemisphere (i.e. heliocentric latitude higher than −50°).Despite the different locations, the spectral patterns of theselected solar bursts are found to be similar between 10 MHzand 2 MHz but unalike at lower frequency. We discuss the variation of theintensity level as recorded by the three spacecraft. We show thatthe reception system of each experiment affected the way the TypeIII burst intensity is measured.Also we attempt to estimate theelectron beam along the interplanetary magnetic fieldwhere the trajectory is an Archimedean spiral. This leads us toinfer on the visibility of the source location with regard to thespacecraft position.

[学科分类] 电子、光学、磁材料