Abstract Saturn’s ring current, which modulates the global magnetic field configuration, varies dynamically with hot plasma injections. However, quantifying transient magnetic field disturbances remains challenging in the absence of in situ measurements on Saturn’s surface. Using a forward simulation method, we extract the energetic ion distributions from energetic neutral atom (ENA) images, thereby estimating the energy content from the suprathermal ring current particles and the corresponding magnetic field disturbance. We analyze a dynamic event and show that suprathermal ring current energy triples after injection, then rapidly decays over the subsequent planetary rotation period. The magnetic field depression at the planetary equator is ∼21nT $mathit{sim }21,nT$ after the injection, which is equivalent to a small geomagnetic storm in Earth’s magnetosphere. Internal plasma sources and neutral gas environment lead to differences between Saturn’s and Earth’s ring current dynamics, revealing the characteristics of giant planet magnetosphere.