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26 April 2024 |
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Establishing a Connection Between Active Region Outflows and the Solar Wind: Abundance Measurements with EIS/Hinode | | David H. Brooks
; Harry P. Warren
; | | Date: |
22 Sep 2010 | | Abstract: | One of the most interesting discoveries of the X-ray Telescope and EUV
Imaging Spectrometer (EIS) on board the Hinode solar observatory is the
presence of persistent high temperature high speed outflows from the edges of
active regions. Measurements by EIS indicate that the outflows reach velocities
of 50 km/s with spectral line asymmetries approaching 200 km/s. It has been
suggested that these outflows may lie on open field lines that connect to the
heliosphere, and that they could potentially be a significant source of the
slow speed solar wind. A direct link has been difficult to establish, however.
In this letter, we use EIS measurements of spectral line intensities that are
sensitive to changes in the relative abundance of Si and S as a result of the
first ionization potential (FIP) effect, to measure the chemical composition in
the outflow regions of AR 10978 over a period of 5 days in December 2007. We
find that Si is always enhanced over S by a factor of 3--4. This is generally
consistent with the enhancement factor of low FIP elements measured in-situ in
the slow solar wind by non-spectroscopic methods. Plasma with a slow wind-like
composition was therefore flowing from the edge of the active region for at
least 5 days. Furthermore, on December 10--11, when the outflow from the
western side was favorably oriented in the Earth direction, the Si/S ratio was
found to match the value measured a few days later by ACE/SWICS. These results
provide strong observational evidence for a direct connection between the solar
wind, and the coronal plasma in the outflow regions. | | Source: | arXiv, 1009.4291 | | Services: | Forum | Review | PDF | Favorites | |
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