Wj. Chaplin et al., LOW-DEGREE, L=4 MODES IN FULL-DISC BISON HELIOSEISMOLOGICAL DATA, Monthly Notices of the Royal Astronomical Society, 280(4), 1996, pp. 1162-1166
We demonstrate that some l=4 acoustic eigenmodes of the Sun are clearl
y distinguishable in long power spectra generated from Doppler velocit
y residuals collected in unimaged sunlight by the six-station Birmingh
am Solar Oscillations Network (BiSON). Modes covering the range n=17 t
o 21 have been measured in 16-month-long power spectra. They have typi
cal amplitudes - when measured in full-disc Doppler velocity data - of
less than similar to 1 cm s(-1) per root bin, and their frequencies h
ave been determined to fractional accuracies of the order of 3 parts i
n 10(5). The sensitivity of the whole-disc observations to these modes
- as implied by the data - appears to be approximately a factor of 2
greater than the theoretical predictions of Christensen-Dalsgaard.