Tu et al. (2005, Science, 308, 519) suggested a scenario of solar wind origin in the coronal funnel. The data analysis in (Tu et al., 2005) is restricted to 25 Mm, at which height Ne VIII emits, due to lacking observations of the coronal above 25 Mm. Thus, it is still unclear whether or not the outflow in the transition region maintains moving upward in the corona. It is needed to reveal the flow information in the corona. One important scientific objective of EIS is to observe flow field in the corona through spectroscopic scanning. SUMER and EIS together provide us an excellent opportunity to obtain a complete physical picture of solar wind origin from the chromosphere to the corona.
In Tu et al (2005), the solar wind outflow is assumed to be launched by reconnection at the networkd boundary between open flux lines and intra-network closed loops. The intra-network closed loops are pushed by supergranular convection toward the network. He et al. (2008, Sol Physics) once set up a numerical model to simulate the upward flow and downward flow in the coronal funnel by assuming that the mass and energy are input into the funnel at 5 Mm after reconnection. Hereto, magnetic cancellation below the strong Ne VIII blue-shifts (solar wind outflow) and supergranular convection around have not been presented. SOT provides us an excellent opportunity to study the magnetic cancellation and supergranula convection near the network, which are suggested to drive the solar wind outflow.
Besides the supergranula convection, photospheric p-mode oscillation may also have some connection with the outflow in open funnel rooted at the network. P-mode oscillation can give rise to spicule [De Pontieu et al., 2004, Nature], and the low-frequency Alfven wave propagates upward along the spicule to provide energy for the solar wind origin [De Pontieu et al., 2007, Science]. Therefore, the Dopplergram observed by SOT is also needed. |
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