Magnetic vortices descending from Jupiter’s ionosphere into its deep atmosphere are believed to trigger the formation of ultraviolet-absorbing anticyclonic storms, according to a study published on November 26 in Nature Astronomy. These storms, appearing as dark ovals, span the size of Earth and have been observed primarily in Jupiter’s polar regions. The phenomenon was first detected in ultraviolet (UV) light by the Hubble Space Telescope in the 1990s and later confirmed by NASA’s Cassini spacecraft in 2000.

Research Unveils Tornado Dynamics

The study, published in the Nature journal, was led by Troy Tsubota, an undergraduate researcher at the University of California, Berkeley, in collaboration with Michael Wong from UC Berkeley, Amy Simon of NASA’s Goddard Space Flight Center, and others.

The findings suggest these dark ovals are formed by swirling magnetic tornadoes generated due to friction between Jupiter’s immense magnetic field lines and those in its ionosphere. These tornadoes are thought to stir aerosols, creating dense patches of UV-absorbing haze in the stratosphere.

The Role of the Io Plasma Torus

The study highlights that Jupiter’s magnetic field, among the strongest in the solar system, interacts with the Io Plasma Torus — a ring of charged particles released by volcanic activity on Jupiter’s moon Io. This interaction generates friction, potentially initiating magnetic vortices that descend into the planet’s atmosphere.

The exact mechanism remains unclear, with researchers debating whether these tornadoes dredge up material from deeper atmospheric layers or create the hazes independently.

Regular Observations Confirm Patterns

The Outer Planet Atmospheres Legacy (OPAL) project, which captures annual images of Jupiter using the Hubble Space Telescope, played a pivotal role in the discovery. Between 2015 and 2022, dark ovals were observed at the south pole in 75% of images but were significantly rarer at the north pole. These formations typically appear over a month and dissipate within two weeks, resembling a magnetic “tornado alley.”