Different density models compared to the results obtained by BELLA. The density models were calibrated using ACE in situ data at 1 au (see Fig. 7, left). The electron density trend shows an approximate negative 1/R² slope, which is consistent with the slope of interplanetary density models. However, the density models were one order of magnitude closer to the Sun than those measured by BELLA. This is consistent with studies that showed that radio scattering makes the apparent source location appear farther from the Sun than their true location (Chrysaphi et al. 2018; Chen et al. 2023).