  The polar cyclone at Jupiter's south pole and the five cyclones surrounding
it oscillate in position and interact. These cyclones, observed since 2016 by
NASA's Juno mission, present a unique opportunity to study vortex dynamics and
interactions on long time scales. The cyclones' position data, acquired by
Juno's JIRAM instrument, is analyzed, showing dominant oscillations with ~12
month periods and amplitudes of ~400 km. Here, the mechanism driving these
oscillations is revealed by considering vorticity-gradient forces generated by
mutual interactions between the cyclones and the latitudinal variation in
planetary vorticity. Data-driven estimation of these forces exhibits a high
correlation with the measured acceleration of the cyclones. To further test
this mechanism, a model is constructed, simulating how cyclones subject to
these forces exhibit similar oscillatory motion.
