The normalized, conditional expectation value of particle energy density as a function of bulk current velocity 〈nγ∣Δv〉/〈nγ〉 is shown for both B₀/δB₀ = 10 and B₀/δB₀ = 1, where Δv = J/en. The energy density is calculated directly from PIC particles with γ > 5 taken at a particular time step. The mean energy density is nearly uncorrelated with Δv for the weak-guide-field case, but is strongly correlated for strong guide fields. For the case B₀/δB₀ = 10, ﹩\tilde{\gamma }=1/\sqrt{1-{\rm{\Delta }}{v}^{2}/{c}^{2}}﹩ is shown in the inset for the same region introduced in Figure 5, with a logarithmically scaled colormap from blue (﹩\tilde{\gamma }\approx 1﹩) to red (﹩\tilde{\gamma }\approx 85﹩).