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The detection of gravity modes is expected to give us unprecedented insightsinto the inner dynamics of the Sun. Within this framework, predicting theiramplitudes is essential to guide future observational strategies and seismicstudies. In this work, we predict the amplitude of low-frequency asymptoticgravity modes generated by penetrative convection at the top of the radiativezone. The result is found to depend critically on the time evolution of theplumes inside the generation region. Using a solar model, we compute the GOLFapparent surface radial velocity of low-degree gravity modes in the frequencyrange $10~\mu H_z\le \nu \le 100~\mu H_z$. In case of a Gaussian plume timeevolution, gravity modes turn out to be undetectable because of too smallsurface amplitudes. This holds true despite a wide range of values consideredfor the parameters of the model. In the other limiting case of an exponentialtime evolution, plumes are expected to drive gravity modes in a much moreefficient way because of a much higher temporal coupling between the plumes andthe modes than in the Gaussian case. Using reasonable values for the plumeparameters based on semi-analytical models, the apparent surface velocities inthis case turn out to be one order of magnitude smaller than the 22-years GOLFdetection threshold and than the previous estimates considering turbulentpressure as the driving mechanism, with a maximum value of $0.05$ cm s${}^{-1}$for $\ell =1$ and $\nu\approx 100~\mu H_z$. When accounting for uncertaintieson the plume parameters, the apparent surface velocities in the most favorableplausible case become comparable to those predicted with turbulent pressure,and the GOLF observation time required for a detection at $ \nu \approx100~\muH_z$ and $\ell=1$ is reduced to about 50 yrs.

Amplitude of solar gravity modes generated by penetrative plumes