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J. M. Pasachoff, B. A. Babcock, K. D. Russell, S. K. May (Williams College--Hopkins Obs.)
We report on CCD observations of the corona from Ramnicu Valcea, Romania, during the total solar eclipse of 11 August 1999. One experiment searched for oscillations in the 530.3-nm coronal green line at about 1 Hz by digitizing at 10 Hz, as a determination of the coronal oscillation spectrum to test models of magnetohydrodynamic heating. The optical system was improved in several ways since the 1998 expedition, as was monitoring of the filter. The series of images was aligned and Fourier transforms were examined for individual pixels and groups of pixels. No oscillations were clearly detected above the 1% level, though statistical analysis continues at this writing. A second experiment took a series of 36 images through one filter wheel that contained three filters near 400 nm and a second filter wheel containing polarizers at three angles plus a parfocal clear filter. The results include a polarization map of a quadrant of the sun and an attempt to map the coronal temperature. The temperature map uses techniques suggested by Cram (1976) through a determination of the extent to which scattering off high-temperature electrons wash out the photospheric Fraunhofer lines. Low-pass filtering of our resultant images show detail in the form of coronal loops but do not show much non-radial structure in the temperature variations. We also compare composite photographic observations with EIT images from eclipse day.
The expedition was supported by NSF grant ATM-9812408, National Geographic Society grant 6449-99, the Keck Northeast Astronomy Consortium, and NASA SOHO/EIT guest-investigator grant NRA-98-03-SEC-051.
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