Rapidly time-varying zonal flow in Jupiter's deep interior

Recently, it has been shown that the secular variation of Jupiter's magnetic field, which has been observed by the Juno spacecraft, is in large part due to eastward advection of the Great Blue Spot (a localized, equatorial region of intense magnetic field) by fluid flow in the deep interior. More recent observations  by Juno suggest that the drift rate of the spot is varying rapidly in time. These time variations can be fit with a sinusoidal variation of the flow speed with a period of approximately four years.  Here, we discuss both the mechanism of this time variability and the constraints that its observability place on the structure and dynamics of the deep interior.