Finite element approximation for a modified anomalous subdiffusion equation

In this paper, we consider a modified anomalous subdiffusion equation (MASFE) for describing processes that become less anomalous as time progresses by the inclusion of a second fractional time derivative acting on the diffusion term. Firstly, a semi-discrete approximation for the MASFE is proposed. The stability and convergence of the semi-discrete approximation are discussed. Secondly, a finite element approximation for the MASFE is derived. The stability and convergence of the finite element approximation are investigated, respectively. Finally, some numerical examples are presented to demonstrate the effectiveness of theoretical analysis.