CORAR reconstruction of a synthetic blob. The location of the blob in the HEE coordinate is 0° in latitude, 30° in longitude, and 10 R_⊙ in heliocentric distance. The number density at the center of the blob is about 3.5 × 10⁴ cm⁻³. The separation angle between the Earth and the spacecraft STEREO-A/B is about 65°/71°. Panel a: coordinates of STEREO-A (STA), STEREO-B (STB), the Sun, and the synthetic blob. The STA-Sun-STB angle (θ_Sun) and the STA-blob-STB angle (θ_blob, namely the opening angle in the text) are highlighted. L_AB is defined as the connecting line of two spacecraft. Panel b: 3D presentation of the synthetic blob. Panels c and d: synthetic COR-2A and COR-2B images containing the blob. Panel e: 3D presentation of cc that represents the reconstructed structure (see the context in Sect. 2). Panel f: reconstructed structure in the X − Y plane. The half thickness r_AB of the reconstructed structure in the direction of L_AB is labeled. Panels g and h: reconstructed structure observed from the COR-2A and COR-2B perspectives. The maximum radii of the reconstructed blob on COR-2A and COR-2B images, i.e., maximum r_A and r_B, respectively, are labeled.