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Gaia Data Release 2 revealed detailed structures of nearby stars in phasespace. These include the Hercules stream, whose origin is still debated. Mostof the previous numerical studies conjectured that the observed structuresoriginate from orbits in resonance with the bar, based on static potentialmodels for the Milky Way. We, in contrast, approach the problem via aself-consistent, dynamic, and morphologically well-resolved model, namely afull $N$-body simulation of the Milky Way. Our simulation comprises about 5.1billion particles in the galactic stellar bulge, bar, disk, and dark-matterhalo and is evolved to 10 Gyr. Our model's disk component is composed of 200million particles, and its simulation snapshots are stored every 10 Myr,enabling us to resolve and classify resonant orbits of representative samplesof stars. After choosing the Sun's position in the simulation, we compare thedistribution of stars in its neighborhood with Gaia's astrometric data, therebyestablishing the role of identified resonantly trapped stars in the formationof Hercules-like structures. From our orbital spectral-analysis we identifymultiple, especially higher order resonances. Our results suggest that theHercules stream is dominated by the 4:1 and 5:1 outer Lindblad and corotationresonances. In total, this yields a trimodal structure of the Hercules stream.From the relation between resonances and ridges in phase space, our modelfavored a slow pattern speed of the Milky-Way bar (40--45 $\mathrm{km \; s^{-1}\; kpc^{-1}}$).

Trimodal structure of Hercules stream explained by originating from bar resonances