Coupled G-Mode Intersections and Solar-Cycle Variability

Abstract

Wolff (Astrophys. J.193, 721, 1974) introduced the concept of g-mode coupling within the solar interior. Subsequently, Wolff developed a more quantitative model invoking a reciprocal interaction between coupled g modes and burning in the solar core. Coupling is proposed to occur for constant values of the spherical harmonic degree [l] creating rigidly rotating structures denoted as sets(l). Power would be concentrated near the core and the top of radiative zone [RZ] in narrow intervals of longitude on opposite sides of the Sun. Sets(l) would migrate retrograde in the RZ as function of l and their intersections would deposit extra energy at the top of the RZ. It is proposed that this enhances sunspot eruptions at particular longitudes and at regular time intervals. Juckett and Wolff (Solar Phys.252, 247, 2008) detected this enhancement by viewing selected spherical harmonics of sunspot patterns within stackplots twisted into the relative rotational frames of various sets(l). In subsequent work, the timings of the set(l) intersections were compared to the sub-decadal variability of the sunspot cycle. Seventeen sub-decadal intersection frequencies (0.63 – 7.0 year) were synchronous with 17 frequencies in the sunspot time-series with a mean correlation of 0.96. Six additional non-11-year frequencies (periods of 8.0 to 28.7 year) are now shown to be nearly synchronous between sunspot variability and the model. Two additional intersections have the same frequency as the solar cycle itself and peak during the rising phase of the solar cycle. This may be partly responsible for cycle asymmetry. These results are evidence that some of the solar-cycle variability may be attributable to deterministic components that are intermixed with a broad-spectrum stochastic and long-term chaotic background.