Planetary scientists have uncovered a fascinating phenomenon on Jupiter: magnetic tornadoes that are spawning giant anticyclonic storms, each about the size of Earth, Space.com reports.
These storms, known as dark ovals, are characterized by dense ultraviolet-absorbing haze and are visible only in UV light. They form in Jupiter’s stratosphere, typically at its poles, and are linked to the planet’s powerful magnetic field.
The dark ovals were first observed by the Hubble Space Telescope in the late 1990s, and later confirmed by NASA’s Cassini spacecraft in 2000. However, the origin of these strange storms remained a mystery until recently. A team of scientists led by undergraduate student Troy Tsubota from the University of California, Berkeley, has now determined that these dark ovals are formed by magnetic vortices, or “magnetic tornadoes,” generated when friction occurs between magnetic field lines in Jupiter’s intense magnetic environment.
The key breakthrough in understanding the formation of these mysterious storms came from analyzing annual images of Jupiter taken by the Hubble Space Telescope between 2015 and 2022. The research was part of NASA’s Outer Planet Atmospheres Legacy (OPAL) project, which monitors the atmospheric changes of the giant planets. These images revealed that dark ovals appeared frequently at Jupiter’s south pole, but much less so at the north pole, providing clues to their magnetic origin.
The formation of these magnetic tornadoes is linked to Jupiter’s complex magnetic field, which converges at the planet’s poles, similar to Earth’s magnetic field. This concentration of magnetic field lines drives charged particles toward the poles, creating auroras. However, unlike Earth’s colorful auroras, Jupiter’s auroras are detectable only in ultraviolet light. The dark ovals, appearing as transitory patches of haze, are thought to be influenced by these auroral dynamics, suggesting a connection to Jupiter’s magnetic activity.
Tsubota and his collaborators, including NASA scientist Amy Simon and planetary experts Michael Wong, Tom Stallard, and Xi Zhang, proposed that the formation of the dark ovals is a result of friction between magnetic field lines in the planet’s ionosphere and the Io Plasma Torus—an enormous ring of charged particles generated by the volcanic activity on Jupiter’s moon, Io. This friction creates swirling magnetic vortices that travel down into Jupiter’s stratosphere, stirring up aerosols and forming the dense, UV-absorbing haze that creates the dark ovals.
Interestingly, the dark ovals appear with a predictable timing, typically forming over a month and dissipating within a couple of weeks. This cyclical nature points to the stability and regularity of the magnetic processes driving these storms, with Jupiter seemingly sitting in the midst of its own “magnetic tornado alley.”
These findings were published in the journal Nature Astronomy on November 26.
