Our primary goal is to understand the nature and origin of the slow solar wind and its relation to coronal streamers. We will characterize solar wind source regions from streamers, including their boundaries and helmet tops. Velocity measurements will be made using Doppler dimming and correlation tracking of plasma blobs in white light. Abundance measurements will be made both in the corona and in the solar wind to track the origin of solar wind streams. In situ and IPS measurements of wind speeds will be used to map the slow wind streams from the Sun to the heliosphere.
We require multiple instruments in order to track the slow wind from its origin in Sun's lower atmosphere, through the corona, and out to interplanetary space. The slow solar wind, while often associated with the streamer belt at solar minimum, most likely originates from more than one type of coronal structure. The various instruments required have capabilities that are suited for probing the Sun in different observational regimes. Instruments with the highest time cadence are best suited for studies of intermittent sources. Spectroscopic instruments are best suited for time averaged observations of steady source regions. The strength of the spectroscopic observations is that they can 'tag' the wind by characterizing the kinetic temperatures, outflow speeds, and abundance composition of the solar wind source regions in the corona. Imaging instruments can provide the best constraints for the magnetic field geometry and also determine electron densities and temperatures. The IPS instruments will provide information on the velocity, density, magnetic field, and spatial distribution of fast and slow wind in the heliosphere. Solar wind instruments on Ulysses and other in situ spacecraft will provide the composition data to make the connections back to the Sun. |
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