Stella Offner edited subsubsection_Bispectrum_Bicoherence_SSRO_no__.tex  over 8 years ago

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For each run, we compute the bicoherence of our integrated intensity maps using the randomly samples sets.   Figure 8 depicts the bicoherence matrices for outputs W1T2t0.2 and T2t0. The bicoherence matrix of W1T2t0.2 exhibits a clear signal on the diagonal, but exhibits little correlation elsewhere. In contrast, the bicoherence maxtrix of T2t0 contains a significant fraction of pixels above 0.5, i.e., there is fairly widespread correlation. If magnetic waves enhance correlation across scales, the wind shells may break up the volume and, thus, reduce correlation. Although shell expansion may perturb the magnetic field and excite magnetosonic waves, it is difficult to see any impact against the background turbulence (OA14). This statistic in fact seems to suggest that the shells reduce correlation perhaps by disrupting the propagation of MHD waves.  This result is surprising considering the trends found by \citep{burkhart10} in their application of the bispectrum of HI data of the SMC. They found that the column density HI maps exhibited enhanced correlation compared to numerical simulations of pure turbulence. They also discovered a break around $\sim 160$ parsecs, which they attribute to supernova feedback. \citep{burkhart10} also show that correlation is much higher for super-Alfvenic turbulence ($\mathcal{M}_A =\sqrt{12\pi \rho} \sigma/B> 1$). The Alfven mach numbers here range from $\sim 1-5.5$. Since the velocity dispersion, and hence the Alfvenic mach number, increases for the strong feedback case, we would apriori expect more correlation. However, we see the opposite. This supports the conclusion that the shells are supressing the free propagation of MHD waves, which would enhance coupling.  %Burhart 2010: For a fixed MA, supersonic models show a higher degree of wave–wave correlations over subsonic models. For a fixed Ms, models with a higher magnetic field (sub-Alfvénic, e.g., = 0.7) show somewhat stronger correlations than the models with a weaker magnetic field (super-Alfvénic) although this difference is not striking.  %We find that the   % run with feedback generates more random phases between signals than that of our run without feedback. SSRO there actually seems to be less correlation in the feedback case -- much higher fraction of blue.