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Spectroscopic Observation of Oscillations in the Corona During the Total Solar Eclipse of 22 July 2009

Singh, Jagdev and Hasan, SS and Gupta, GR and Nagaraju, K and Banerjee, D (2011) Spectroscopic Observation of Oscillations in the Corona During the Total Solar Eclipse of 22 July 2009. In: Solar Physics, 270 (1). pp. 213-233.

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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 30A degrees 28.1' N; longitude 119A degrees 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 mu m 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 x 1k CCD cameras, with a pixel size of 13 mu m 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 Alfv,n 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.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Springer.
Keywords: Coronal heating;Emission lines;MHD waves;Oscillations;Solar corona
Department/Centre: Division of Physical & Mathematical Sciences > Joint Astronomy Programme
Date Deposited: 30 May 2011 06:22
Last Modified: 02 Nov 2011 06:03
URI: http://eprints.iisc.ernet.in/id/eprint/38038

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