NASA's Juno spacecraft data reveals 'giant swirling waves' at Jupiter’s magnetosphere

The occurrence of these giant waves

The scientists found that the gigantic waves are most likely caused by a significant change in velocity near the magnetopause, which is the boundary between the planet's magnetic field and the solar wind. 

This velocity differential may result in the formation of a swirling pattern wave known as Kelvin-Helmholtz. As per the official statement, only instrument-based data from plasma and magnetic fields can reveal the presence of these invisible waves. 

“Kelvin-Helmholtz instabilities are a fundamental physical process that occurs when solar and stellar winds interact with planetary magnetic fields across our solar system and throughout the universe,” explained Jake Montgomery, a doctoral student in the joint space physics program between UTSA and SwRI, in an official release.

The team gathered information from Juno's numerous research equipment, including the magnetometer and the Jovian Auroral Distributions Experiment (JADE).

Montgomery added: “Juno observed these waves during many of its orbits, providing conclusive evidence that Kelvin-Helmholtz instabilities play an active role in the interaction between the solar wind and Jupiter.”

Way back in 1868, a German biologist and physicist, Hermann von Helmholtz, first found these instabilities.

In general, the Kelvin-Helmholtz instabilities may be seen in the atmospheres of several planets, including ours, in the cloud formations on Earth. It also likely occurs in the massive Red Spot on Jupiter, as well as the atmosphere of the Sun.

The study results have been reported in the journal Geophysical Research Letters. 

Study abstract:

We use the Kelvin-Helmholtz instability (KHI) condition with particle and magnetic field observations from the Jovian Auroral Distributions Experiment and MAG on Juno along the dawn flank of Jupiter's magnetosphere. We identify the occurrence of magnetopause crossings that show evidence of being KH (Kelvin-Helmholtz) unstable. When estimating the k vector to be parallel to the velocity shear, we find that 25 of 62 (40%) magnetopause crossings satisfy the KHI condition. When considering the k vector of the maximum growth rate through a solid angle approach, we find that 60 of 62 (97%) events are KH unstable. This study shows evidence of KH waves at Jupiter's dawn flank, including primary drivers such as high-velocity shears and changes in plasma pressure. Signatures of magnetic reconnection were also observed in ∼25% of the KH unstable crossings. We discuss these results and their implication for the prevalence of KHI at Juno's dawn magnetopause as measured by Juno.