| Abstract: | We performed high resolution spectroscopy of the solar corona during the total solar eclipse of 22 July 2009 in two emission
lines: the green line at 5303 ? due to Fe xiv and the red line at 6374 ? due to Fe x, simultaneously from Anji (latitude 30°28.1′ N; longitude 119°35.4′ E; elevation 890 m), China. A two-mirror coelostat with
100 cm focal length lens produced a 9.2 mm image of the Sun. The spectrograph using 140 cm focal length lens in Littrow mode
and a grating with 600 lines per millimeter blazed at 2 μm provided a dispersion of 30 m? and 43 m? per pixel in the fourth
order around the green line and third order around the red line, respectively. Two Peltier cooled 1k × 1k CCD cameras, with
a pixel size of 13 μm square and 14-bit readout at 10 MHz operated in frame transfer mode, were used to obtain the time sequence
spectra in two emission lines simultaneously. The duration of totality was 341 s, but we could get spectra for 270 s after
a trial exposure at an interval of 5 s. We report here on the detection of intensity, velocity, and line width oscillations
with periodicity in the range of 25 – 50 s. These oscillations can be interpreted in terms of the presence of fast magnetoacoustic
waves or torsional Alfvén waves. The intensity ratios of green to red emission lines indicate the temperature of the corona
to be 1.65 MK in the equatorial region and 1.40 MK in the polar region, relatively higher than the expected temperature during
the low activity period. The width variation of the emission lines in different coronal structures suggests different physical
conditions in different structures. |
