Magnetic tornadoes on Jupiter

For centuries, the Great Red Spot has been the best-known feature of the planet Jupiter. However, there are other equally large spots at the planet’s north and south poles. These dark, oval-shaped spots, which appear and disappear seemingly at random, are only visible in ultraviolet light. Astronomers have documented them extensively for the first time.

These mysterious ovals, each as large as Earth, are found in layers of stratospheric haze that cover the planet’s poles.

The dark ovals, when visible, are almost always located just below the areas of each pole in which quite bright auroras occur. These are similar to the northern and southern lights on Earth.

These oval-shaped spots absorb more ultraviolet light than the surrounding area, which makes them appear dark in images taken in this band by telescopes such as the Hubble space telescope of the American and European space agencies (NASA and ESA).

In annual photographs of the planet taken by Hubble between 2015 and 2022, a dark oval in ultraviolet light appears 75% of the time at the south pole, while dark ovals only appear in one of eight images captured of the north pole. .

The dark ovals denote unusual processes taking place in Jupiter’s strong magnetic field and propagating toward the poles and deep into the atmosphere, much deeper than the magnetic processes that produce auroras on Earth.

The phenomenon has been documented and analyzed in a new study by a team including, among others, Troy K. Tsubota and Michael Wong, both from the University of California at Berkeley, United States, as well as Tom Stallard, from the University of Northumbria in the United Kingdom.

Jupiter in ultraviolet light, depicted in false colors. In addition to the Great Red Spot, which appears blue here, another oval can be seen in the brown haze at Jupiter’s south pole. These ultraviolet-dark eggs also appear periodically at the North Pole, although less frequently. (Image: Troy Tsubota/Michael Wong/UC Berkeley)

The study’s authors believe the dark oval is likely being churned up from above by a vortex created when the planet’s magnetic field lines experience friction in two very distant places: in the ionosphere, where Stallard and other astronomers previously detected the spinning motion. using ground-based telescopes, and in the thin layer of hot, ionized plasma around the planet released from the volcanic moon Io.

The vortex spins faster in the ionosphere, progressively weakening as it reaches deeper layers. Like a tornado in Earth’s weather when it hits dusty land, the deep end of the vortex stirs up the hazy atmosphere, creating the dense patches seen. It is unclear whether the process drags in more haze from below or generates more haze.

Based on observations, the team suspects that the ovals form over the course of a month and dissipate within a couple of weeks.

The haze in the dark ovals is about 50 times thicker than the typical concentration, suggesting that it likely forms due to eddy dynamics rather than chemical reactions triggered by high-energy particles from the upper atmosphere.

Observations made by the team showed that the timing and location of these energetic particles do not correlate with the appearance of the dark ovals.

The study is titled “UV-dark polar ovals on Jupiter as tracers of magnetosphere–atmosphere connections.” And it has been published in the academic journal Nature Astronomy. (Fountain: NCYT by Amazings)