On the Characteristics of the Solar Gravity Mode Frequencies

Abstract

Gravity modes are the best probes for studying the dynamics of the solarradiative zone, and especially the nuclear core. This paper shows howspecific physical processes influence the theoretical g-mode frequenciesfor the l = 1 and l = 2 modes over a large range of radial orders n from-46 to -1, corresponding to potential SOHO observations. To this end, wecompute different solar models, and we calculate the correspondingtheoretical g-mode frequencies. These frequencies are sensitive to thephysical inputs of our solar models in the high-frequency range of theoscillation power spectrum. At low frequency, we demonstrate that theperiodic spacing (Delta P-l) between two g-modes with consecutive ordersn and with the same angular degree l does not vary significantly fromone model to the other. For all the models considered, including modelsbased on recent solar chemical abundances, the value of thecharacteristic quantity P-0, the fundamental period of the g-modes, isconstant within a 1 minute range (between 34 and 35 minutes). Thisresult is in sharp contrast to the situation before the launch of theSOHO spacecraft, when the dispersion for P-0 was large (with valuesranging from 29 to 60 minutes). Then, we estimate the sensitivity of theoscillation frequency splittings to the solar core rotation. Finally, wereview some features of the g-mode observations obtained with the GOLFinstrument and based on an almost complete solar cycle. Some of thesehelp us constrain the excitation mechanisms of g-modes.