Authors: Emily Mason (PSI), Cooper Downs (PSI), James Turtle (PSI), Ron Caplan (PSI), Jon Linker (PSI)

Coronal hole boundary detection is a critical and active area of research, complicated by the lack of definitive knowledge of the actual magnetic open-closed boundary. Coronal hole observations fall far short of accounting for the heliospheric open flux measured at 1 AU. A lack of observations covering the polar regions and the unknown contributions of open flux corridors near large flux concentrations add to the difficulty in accounting for the Sun’s total open flux via traditional extreme ultraviolet observations. CHMAP (Caplan et al. 2016, 2023) approaches this challenge by incorporating minimum-intensity disk merge (MIDM), a method that compares several images with slightly different lines of sight and selects the darkest pixels, subject to a limb proximity quality measure. MIDM results in coronal holes with boundaries enlarged by the most direct viewpoint available at any time, whether that is from several sequential time steps of one instrument or a combination of spacecraft (i.e., SDO and STEREO). Here, we present a statistical analysis of the amount by which MIDM results in enlarged coronal hole boundaries compared to standard synoptic map methods over the years 2011-2023, providing an overview of how the method acts over an entire solar cycle’s span.