Analysis of the solar cycle and core rotation using 15 years of Mark-I observations:1984-1999. I. The solar cycle

Abstract

High quality observations of the low-degree acoustic modes (p-modes) exist for almost two complete solar cycles using the solar spectrophotometer Mark-I, located at the Observatorio del Teide (Tenerife, Spain) and operating now as part of the Birmingham Solar Oscillations Network (BiSON). We have performed a Fourier analysis of 30 calibrated time-series of one year duration covering a total period of 15 years between 1984 and 1999. Applying different techniques to the resulting power spectra, we study the signature of the solar activity changes on the low-degree p-modes. We show that the variation of the central frequencies and the total velocity power (TVP) changes. A new method of simultaneous fit is developed and a special effort has been made to study the frequency-dependence of the frequency shift. The results confirm a variation of the central frequencies of acoustic modes of about 450 nHz, peak-to-peak, on average for low degree modes between 2.5 and 3.7 mHz. The TVP is anti-correlated with the common activity indices with a decrease of about 20% between the minimum and the maximum of solar cycle 22. The results are compared with those obtained for intermediate degrees, using the LOWL data. The frequency shift is found to increase with the degree with a weak l-dependence similar to that of the inverse mode mass. This verifies earlier suggestions that near surface effects are predominant.

Accepted by A&A October 3 2001

Cited by in corpus (14)

• Changes in Solar Dynamics from 1995 to 2002
• The onset of solar cycle 24: What global acoustic modes are telling us
• Stellar magnetic activity and variability of oscillation parameters - An investigation of 24 solar-like stars observed by Kepler
• Seismic sensitivity to sub-surface solar activity from 18 years of GOLF/SoHO observations
• Quasi-Biennial variations in helioseismic frequencies: Can the source of the variation be localized?
• Influence of Low-Degree High-Order p-Mode Splittings on the Solar Rotation Profile
• The Quasi-Biennial Periodicity (QBP) in velocity and intensity helioseismic observations
• Dynamics of the fast solar tachocline: I. Dipolar field
• An Upper Limit on the Temporal Variations of the Solar Interior Stratification
• On the frequency dependence of p-mode frequency shifts induced by magnetic activity in Kepler solar-like stars
• The Sun's interior structure and dynamics, and the solar cycle
• Damping and excitation variations of the solar acoustic modes using LOWL observations
• Solar cycle variations of large frequency separations of acoustic modes: Implications for asteroseismology
• Distortion of the p-mode peak profiles by the solar-cycle frequency shifts: do we need to worry?