positive contribution to the skewness; see Section \[secBispecDef\]. This is consistent with the positive skewness of the data; see Figure \[figDataExamples\]. The peak in the bispectrum coincides with the peak in the bicoherence. The coupling modes that produce the strongest nonlinearity therefore also result in the largest contribution to the positive skewness in the data.

A positive sign in the bispectral coherence at wave vectors similar to hexagons indicates that the divergence field is preferentially given by outflows surrounded by a network of inflows (see the patterns discussed in Section \[secPatternsIntro\]). The outflows are on average slightly stronger while the inflows occupy a larger area. However, in individual realizations of the data, the phase of $X^{(j)}(\bk) X^{(j)}(\bl) X^{(j)*}(\bmm)$ varies substantially. As a consequence, the opposite case of inflows surrounded by outflows is also present in the data, which can be seen in Figure \[figDataExamples\].

In addition, there are regions with negative bispectrum and bicoherence. In those regions, the three vectors $\bk,\bl,\bmm$ are approximatively parallel, with one component being nearly twice as long as the other two. Figure \[figbicohall\] shows one example for this in the central feature in the central panel ($|\bmm R_\sun|=310.9$, at $\bk=\bl=\bmm/2$). Due to the symmetry relations 