Abstract Extensive time series of resolved solar images have been available for helioseismological studies since the late 1970s. We will first review the temporal coverage that has been built up over the past 11 years at several different observatories. Next, we will present examples of the frequencies, power levels, modal energies, and widths of solar intermediate-(5< ℓ <120) and high-degree (120< ℓ <600) p-modes which were obtained at the Mount Wilson Observatory's 60-Foot Solar Tower Telescope during the rising phase of the current sunspot cycle. We will demonstrate that the inclusion of frequency splittings from the high-degree p-modes has allowed us to demonstrate that the sun's internal equatorial angular velocity is not constant with radius but rather varies systematically with radius throughout the solar convection zone and below. Lastly, we will show that, by intercomparing many of the available p-mode frequency datasets, we have been able to confirm the recent suggestion by Libbrecht and Woodard /1/ that the frequencies of the intermediate-degree p-modes do vary systematically with varying levels of solar activity. In particular, we will demonstrate that such frequency shifts have been occurring in every year that observations have been obtained since 1980 and that such variations are also consistent with similar variations that have been recently noted in low-degree p-mode frequencies.
Observations of intermediate- and high-degree p-mode oscillations during sunspot cycles 21 and 22
Advances in Space Research ; 11 , 4 ; 17-28
1991-01-01
12 pages
Article (Journal)
Electronic Resource
English
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