Parameter space of magnetic field strength as a function of thermal and non-thermal X-ray volumes, with the blue contours indicating specific magnetic field strength. The pink line indicates equal thermal and non-thermal source volumes. The top x-axis indicates n₀ values, which depend directly on V₀ (via Eq. (4)). The red lines indicate the volumes at which specific ratios of thermal to non-thermal electron densities (N/n₀) occur (as indicated). The green shaded area shows the range of magnetic fields possible, given particular constraints on the volumes and ratios of N/n₀. The blue circle with the error bar is the magnetic field strength calculated from the numerical model below.