Solar model: Element diffusion or metal-enhanced envelope?

Solar models with moderate enrichment of heavy elements in the convective e nvelope (CSM) and with element diffusion (DSM) are investigated using updat ed input physics. It is found that both CSM and DSM can result in adequate depth of the convection zone and appropriate surface helium abundance, and the agreement between the calculated and observed p-mode frequencies are al so improved. The sound speed of DSM is better than CSM and the standard sol ar model (SSM) in the deep interior, which means that element diffusion hel ps improve the sound speed profile in the solar interior. In the area just below the base of the convection zone, CSM is the best of the three models.