Radial dependence of spectral slopes and the spectral break frequency of solar wind turbulence near Mercury’s orbit. (a) and (b) show the distributions of magnetic field spectral slopes in the inertial and kinetic ranges, respectively, as functions of heliocentric distance from 0.31 to 0.47 au. Dots denote the median values, and error bars represent the first and third quartiles. (c) and (d) show the radial dependence of the spectral break frequency. In (c), the break frequency is shown in Hz, while in (d) it is normalized by the proton cyclotron frequency ﹩{f}_{\mathrm{cp}}﹩. Dashed curves indicate power-law fits of the form ﹩{\mathrm{ar}}^{b}﹩.