Multi-fluid models and UV observations of coronal streamers
Abstract
The sources of the slow solar wind were long associated with coronal streamers through empirical connections from remote sensing and in-situ observations, and modeling. Near solar activity minimum the solar magnetic field is dominated by a tilted dipole and forms a streamer belt due to the outflow of the slow solar wind. Parker Solar Probe (PSP) will likely provide for the first time in-situ measurements in the stalks of streamers at perihelia. It has been found from Ulysses/SWICS observation that the signatures of the slow and fast solar wind could be identified by heavy ion abundances ratio. UV observations close to the Sun by the Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO during the 1996 minimum activity has demonstrated that the streamer belt structure depends strongly on the observed emission lines, such as H I Ly alpha or O VI ions. Subsequent analysis and 2D multi-fluid modeling have shown that the variability of the heavy ion intensity in various parts of the streamers is associated with regions of slow solar wind outflow. We report the results of 3D multi-fluid models of coronal streamer belt and the associated emissivities of H I Ly alpha, O VI, and other heavy ions computed from the model results. We compare the results of the models with solar minimum observations and find good qualitative agreement. The 3D multi-fluid model allows computing the important line-of-sight integration effects on the observed streamer structure in the plane of the sky in the UV ion emission lines. The model shows the associations between the heavy ion properties in the cores and legs of streamers, and the slow solar wind outflow regions in realistic streamer belt structure, as well as in more realistic magnetic structure based on solar magnetogram boundary conditions. The results could be useful for understanding future PSP data.
- Publication:
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Solar Heliospheric and INterplanetary Environment (SHINE 2019)
- Pub Date:
- May 2019
- Bibcode:
- 2019shin.confE.197O