Fig. 3: Numerical simulation of the MHD lensing process at t/t₀ = 0.185 based on the observed geometric shape of the CH.

The simulation domain includes a background coronal plasma (light blue) and the CH that acts as an MHD lens (blue), as shown in the total energy density (\({{{{{{{\mathcal{H}}}}}}}}/{p}_{0}\)). A single-period fast-mode MHD wave is launched to the left of the CH, which propagates with a circular wavefront initially. After being reflected/transmitted, the initial circular wavefront presents a complex pattern that senses the geometric shape at the CH edges. The initial wavefront, the reflected wavefront by the CH, the transmitted wave, and the focal point are annotated by black arrows. The values of normalization factors p₀, t₀, L₀ for the total energy density (\({{{{{{{\mathcal{H}}}}}}}}\)), time (t) and length (x, y, z) are listed in Table 1. The red dot represents the location of the wave source, and it retains the same meaning in the subsequent Figures. (An animation Video II of this figure is available).