The standard MNE pipeline by uses MNE or dSPM as the inverse method by default. These methods employ the (weighted) ℓ2-norm of the current distribution as regularizer. The important practical benefit of such ℓ2 solvers is that the inverse problem is linear and, therefore, the solution is obtained by multiplying the data with a matrix, called the inverse operator. Once the inverse operator has been constructed, it can be applied to evoked, epochs, and raw data containers. The output of these inverse solvers, as well as all alternative inverse methods, is provided as instances of the SourceEstimate object that can be saved to disk as .stc files. The acronym stc stands for source times courses.
