## 3 Results and Discussion
### Volume Fraction of Minor Components  
Figure 6 shows that the radiometric properties changed with the volume fraction of the minor component for particle aggregates with refractive indices. The particle aggregate is of the structure in Figure 2a. The particle radius in these computations was set to 2 \(\upmu\)m. The spectrum-averaged radiometric properties were averaged at wavelengths of 6.5-10 \(\upmu\)m.  
Figure 6b shows the absorption efficiency. The absorption efficiency generally increases with the volume fraction due to the increase in the volume of the minor component, which is more absorptive relative to the major component. In Mode B with \(m_{2}=0.15+3.15\)i and \(m_{2}=1.46+2.75\)i, the absorption efficiency increases drastically as the volume fraction changes from 0.02 to 0.1 and levels off as the volume fraction exceeds 0.1, indicating that initially adding a small amount of the minor component into each particle of the aggregate can significantly increase the radiation absorption of the aggregate. However, in Mode A with \(m_{2}=0.15+3.15\)i and \(m_{2}=1.46+2.75\)i, the absorption efficiency increases steadily with volume fraction. In Mode B, the minor component spreads evenly into each particle. As explained in Section 3.1, the absorption grows exponentially with optical length [1; 52], while the EMA increases the effective optical length by the mean field approximation, which increases the weak  
Figure 6: Radiometric properties of the particle aggregate changed with the volume fraction of the minor component of different refractive indices. The particle radius is 2 \(\upmu\)m. (Square symbol: Mode A, with the minor component particles randomly positioned; circle symbol: Mode B; black symbol: minor component \(m_{2}=3.102+0.0925\)i; red symbol: minor component \(m_{2}=1.46+2.75\)i; blue symbol: minor component \(m_{2}=0.15+3.15\)i). (**a**) Extinction efficiency; (**b**) absorption efficiency; (**c**) scattering efficiency; (**d**) asymmetric parameter. absorption of the major component, while in Mode A, the minor component only exists in a few particles, and radiation absorption is enhanced in a few spots in the aggregate. Increasing the volume fraction of the minor component or the number of minor component particles causes a steady increase in the absorption efficiency of the aggregate. For \(m_{2}=3.102+0.0925\)i, the minor component is slightly larger in absorption than the major component. Spreading the minor component into each particle (Mode B) has an effect on the increase in the absorption efficiency of the aggregate that is similar to that of concentrating it in a few particles (Mode A); therefore, both Mode A and Mode B show a steady increase in the absorption efficiency with the volume fraction. Figure 6c shows the scattering efficiency. The scattering efficiency generally decreases with the volume fraction of the minor component, and the changes in scattering efficiency seem to be complementarily correlated to the changes in absorption in Figure 6b. The scattering efficiency drops significantly, while the absorption efficiency increases significantly as the volume fraction changes from 0.02 to 0.1. Figure 6d shows the asymmetric parameter. For the asymmetric parameter, the changes that occur with the increase in volume fraction are similar to those that occur with the increase in absorption efficiency in Figure 6b, showing that the asymmetric efficiency is closely related to absorption efficiency. Figure 6a shows the extinction efficiency, which is the sum of the absorption efficiency and scattering efficiency. The absorption efficiencies are similar in different aggregate modes with different refractive indices of the minor component; this is because the difference between Mode A and Mode B in the absorption efficiency in Figure 6a offsets that in the scattering efficiency in Figure 6b.