The Contribution of Planetary Period Oscillations Toward Circulation and Mass Loss in Saturn's Magnetosphere

Abstract

AbstractMagnetic reconnection is a process during which magnetic energy is released as kinetic energy. It is considered a crucial driver of energy transport and mass loss within Saturn's magnetosphere. On long‐term timescales, is thought to be predominantly driven by the rapid rotation of equatorially mass‐loaded flux tubes (i.e., the Vasyliunas cycle), but there is some non‐negligible driving from the solar wind as well (i.e., the Dungey cycle). In this study, we investigate an atmospheric driven phenomenon that modulates Saturn's magnetosphere every ∼10.6–10.8 hr, known as planetary period oscillations (PPOs), as an additional driver of magnetic reconnection at Saturn. Using an empirical model of PPO dynamics and Cassini magnetic field and plasma measurements, we find that PPO‐driven magnetic reconnection is likely to occur in Saturn's magnetosphere, however, the occurrence of the phenomenon depends on temporally variable characteristics of the PPO systems and spatial asymmetries within Saturn's equatorial magnetosphere. Thus, it is not expected to be an on‐going process. On year‐long timescales, we find that PPOs are expected to be on par with the Dungey Cycle in driving circulation within Saturn's magnetosphere. However, on ∼1–2 weeks‐long timescales, under specific conditions where PPO‐driven reconnection is expected to be active, this phenomenon can become more significant than the Vasyliunas cycle, and thus dominate circulation within Saturn's magnetosphere. On year‐long timescales, this process is estimated to remove upwards of ∼20% of the mass loaded into the magnetosphere by Enceladus.