GONG p-Mode Parameters Through Two Solar Cycles
Abstract
We investigate the parameters of global solar p-mode oscillations, namely damping width Γ , amplitude A , mean squared velocity «v2», energy E , and energy supply rate d E /d t , derived from two solar cycles' worth (1996 - 2018) of Global Oscillation Network Group (GONG) time series for harmonic degrees l =0 -150 . We correct for the effect of fill factor, apparent solar radius, and spurious jumps in the mode amplitudes. We find that the amplitude of the activity-related changes of Γ and A depends on both frequency and harmonic degree of the modes, with the largest variations of Γ for modes with 2400 μ Hz≤ν ≤3300 μ Hz and 31 ≤l ≤60 with a minimum-to-maximum variation of 26.6 ±0.3 % and of A for modes with 2400 μ Hz≤ν ≤3300 μ Hz and 61 ≤l ≤100 with a minimum-to-maximum variation of 27.4 ±0.4 % . The level of correlation between the solar radio flux F10.7 and mode parameters also depends on mode frequency and harmonic degree. As a function of mode frequency, the mode amplitudes are found to follow an asymmetric Voigt profile with νmax=3073.59 ±0.18 μ Hz. From the mode parameters, we calculate physical mode quantities and average them over specific mode frequency ranges. In this way, we find that the mean squared velocities «v2» and energies E of p modes are anticorrelated with the level of activity, varying by 14.7 ±0.3 % and 18.4 ±0.3 % , respectively, and that the mode energy supply rates show no significant correlation with activity. With this study we expand previously published results on the temporal variation of solar p-mode parameters. Our results will be helpful to future studies of the excitation and damping of p modes, i.e., the interplay between convection, magnetic field, and resonant acoustic oscillations.
- Publication:
-
Solar Physics
- Pub Date:
- November 2018
- DOI:
- 10.1007/s11207-018-1370-x
- arXiv:
- arXiv:1810.09324
- Bibcode:
- 2018SoPh..293..151K
- Keywords:
-
- Helioseismology;
- observations;
- Oscillations;
- solar;
- Solar Cycle;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in Solar Physics. 33 pages, 16 figures, 5 tables