Planetary scientists have issued a tornado warning for Jupiter following the discovery of magnetic vortices descending from the planet's ionosphere into its deep atmosphere, resulting in giant anticyclones that absorb ultraviolet light, each comparable in size to Earth.
These anticyclonic storms, visible as dark ovals in Jupiter's stratosphere, were first observed in ultraviolet light by the Hubble Space Telescope in the late 1990s, and confirmed at the north pole by NASA's Cassini spacecraft in 2000. However, their formation remained a mystery.
Research led by Troy Tsubota from the University of California, Berkeley, has revealed that these dark ovals are created by swirling magnetic tornadoes generated through friction between magnetic field lines in Jupiter's powerful magnetic field.
The breakthrough came from analyzing images obtained through the Outer Planet Atmospheres Legacy (OPAL) project, which tracks changes in the appearances of the giant planets. Tsubota noted that Hubble's annual imaging provided essential insights into the phenomenon.
From 2015 to 2022, Tsubota identified dark ovals at Jupiter's south pole in three-quarters of the images, while only one instance was noted at the north pole. The concentration of Jupiter's magnetic field at its poles drives charged particles toward these regions, leading to auroras detectable only in ultraviolet light.
To further understand the dark ovals, Tsubota collaborated with Michael Wong and other planetary scientists. They proposed that friction between magnetic field lines in the Io Plasma Torus—a ring of charged particles from Jupiter's volcanic moon, Io—and those in the ionosphere could generate magnetic vortices that extend deep into Jupiter's stratosphere. This interaction could stir aerosols, forming the dense, ultraviolet-absorbing haze characteristic of the dark ovals.
Current observations indicate that the haze within these ovals is significantly denser than typical atmospheric concentrations, suggesting that vortex dynamics play a crucial role in their formation rather than chemical reactions. The dark ovals appear to take about a month to form and dissipate within weeks, indicating a regularity that suggests Jupiter resides in a 'magnetic tornado alley.'