It has been realized that the solar chromosphere often exhibits strong super-sonic flows, especially around a sunspot, driven by magnetic fields, such as strong downflows along a dark filament near its footpoints (Lites 2005, Katsukawa et al. 2010), inverse Evershed flows in a penumbral chromosphere (e.g. Tsiropoula 2000), and penumbral microjets (Katsukawa et al. 2007). It is still poorly known how these flows are driven in the presence of magnetic fields. An important ingredient in acceleration of the flows is strong magnetic and gas pressure gradient. The other possibility is magnetic reconnection, in which magnetic tension force drives Alfvenic flows. It is essential to investigate how the flow velocities are dependent to thermal and magnetic conditions in the chromosphere.
The primary objective of this program is to identify super-sonic flows in the chromosphere around a sunspot, and to investigate how the flow velocities are related with magnetic field configuration and plasma condition. For this purpose, we are going to carry out an observation using Facility Infrared Spectropolarimeter (FIRS) and Interferometric BIdimensional Spectrometer (IBIS) at the Dunn Solar Telescope (DST) of the National Solar Observatory. The observation is expected to provide He I 1083 nm Stokes profiles with FIRS and spectral profiles of the Ca II 854 nm line with IBIS. We would like to propose a Hinode observation coordinated with DST to get information of photospheric magnetic fields at 630 nm and chromospheric activities at BFI Ca II H with SOT. XRT and EIS observations are also requested to get the information of the coronal structures and flows above a sunspot. |
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