  Brown dwarfs were recently found to display rotational modulations, commonly
attributed to cloud cover of varying thickness, possibly modulated by
planetary-scale waves. However, the long-term, continuous, high-precision
monitoring data to test this hypothesis for more objects is lacking. By
applying our novel photometric approach to TESS data, we extract a
high-precision lightcurve of the closest brown dwarfs, which form the binary
system Luhman 16AB. Our observations, that cover about 100 rotations of Luhman
16B, display continuous lightcurve evolution. The periodogram analysis shows
that the rotational period of the component that dominates the lightcurve is
5.28 h. We also find evidence for periods of 2.5 h, 6.94 h, and 90.8 h. We show
that the 2.5 h and 5.28 h periods emerge from Luhman 16B and that they consist
of multiple, slightly shifted peaks, revealing the presence of high-speed jets
and zonal circulation in this object. We find that the lightcurve evolution is
well fit by the planetary-scale waves model, further supporting this
interpretation. We argue that the 6.94 h peak is likely the rotation period of
Luhman 16A. By comparing the rotational periods to observed v sin(i)
measurements, we show that the two brown dwarfs are viewed at angles close to
their equatorial planes. We also describe a long-period (P~91 h) evolution in
the lightcurve, which we propose emerges from the vortex-dominated polar
regions. Our study paves the way toward direct comparisons of the predictions
of global circulation models to observations via periodogram analysis.
