  We report on a search for short-period intensity variations in the green-line
FeXIV 530.3 nm emission from the solar corona during the 21 August 2017 total
eclipse viewed from Idaho in the United States. Our experiment was performed
with a much more sensitive detection system, and with better spatial
resolution, than on previous occasions (1999 and 2001 eclipses), allowing fine
details of quiet coronal loops and an active-region loop system to be seen. A
guided 200-mm-aperture Schmidt-Cassegrain telescope was used with a
state-of-the-art CCD camera having 16-bit intensity discrimination and a
field-of-view 0.43 degree x 0.43 degree that encompassed approximately one
third of the visible corona. The camera pixel size was 1.55 arcseconds, while
the seeing during the eclipse enabled features of approx. 2 arcseconds (1450 km
on the Sun) to be resolved. A total of 429 images were recorded during a 122.9
second portion of the totality at a frame rate of 3.49 images per second. In
the analysis, we searched particularly for short-period intensity oscillations
and travelling waves, since theory predicts fast-mode magneto-hydrodynamic
(MHD) waves with short periods may be important in quiet coronal and
active-region heating. Allowing first for various instrumental and photometric
effects, we used a wavelet technique to search for periodicities in some 404
000 pixels in the frequency range 0.5-1.6 Hz (periods: 2 second to 0.6 second).
We also searched for travelling waves along some 65 coronal structures.
However, we found no statistically significant evidence in either. This
negative result considerably refines the limit that we obtained from our
previous analyses, and it indicates that future searches for short-period
coronal waves may be better directed towards Doppler shifts as well as
intensity oscillations.
