The Jovian Auroras

By Udita Shukla 

When charged particles emitted by the sun from its (solar) flares and (solar) winds reach the earth, they are acted upon by the protective magnetic field (magnetosphere) enveloping the planet. Charged particles like electrons and protons, by nature, deflect in the presence of magnetic field, along with the magnetic lines. They get smashed into gas molecules and get accelerated in the process, thereby, emitting various wavelengths (colours) of light. This spectacular light show in the polar sky is what is called Aurora Borealis (in the Northern Hemisphere) and Aurora Australis (Southern Hemisphere).

Studying the auroras

A similar phenomenon occurs at the poles of Jupiter. Scientists have long been studying the exact cause and mechanism of Jovian auroras. A recent discovery by the National Aeronautics and Space Administration (NASA) spacecraft, Chandra X-ray Observatory and XMM-Newton, has found that the northern and southern Jovian auroras are perfectly out of sync with each other. This means, that these lights behave completely independent of one another. The study, led by William Dunn and Andrew Coates from University College London has unearthed some unexpected tantrums from the Jovian auroras. Strangely enough, the southern aurora danced every nine to twelve minutes, the northern aurora seemed to show a rather erratic and whimsical movement. Additionally, the brightness of the two (auroras) also varied from one pulse to the next. The finding has baffled astrophysicists because both the northern and southern auroras had been anticipated to be influenced by the same causes, that is, magnetic field and charged particles. As per Jonathan Nichols from the University of Leicester, “You might imagine that what affects the auroras in the north would affect the auroras in the south,”.

Benefits of research

A better understanding of such phenomena will enable scientists to decode the working of its atmosphere, perhaps a new perspective on how charged particles interact with extreme magnetic fields. The research bears profound implications on the understanding of how the sun and other sources influence auroras. Moreover, since auroras are the direct product of the presence of a planet’s magnetosphere, they are considered as the signature of its (the planet’s) magnetic field. Delving deep into the heart of Jupiter’s auroras will give clues as to how other planets work and behave. 

It is tremendously important to know and understand the working of other planets in the solar system because it will further help us unravel the secrets of other life-supporting planets in the universe. Planetary exploration and extraterrestrial life is an area of active research. In the words of William Dunn, “If we’re going to search other planets for other life, then we’re going to want to find places that have magnetic fields,”. “Understanding in our Solar System what the signatures for northern lights are and what they mean is important, because hopefully at some point in the future, we’ll be looking at these signatures at extra-solar planets.”

Jupiter and auroras

On Jupiter, charged particles are thought to be reaching from the sun as well as volcanic activity from Jupiter’s moon, Io. Due to the high rotational speed of the planet, highly charged molecules of carbon, sulphur, oxygen and carbon align along the magnetic field lines, are accelerated to tons of megavolts of energy before being bombarded with the particles in the atmosphere. This collision extracts away electrons from these molecules and results in the generation of high-energy X-rays. According to Coates, “Everything is happening in a supercharged way”. Given that Jupiter’s magnetosphere is stronger than the earth’s, the X-ray activity is also stronger there than it is back home.  

Jupiter is not the only planet under the radar. Recently, Mars and Saturn have been visited by unmanned spacecrafts that have brought back immense information, data and visuals. While the Martian atmosphere has divulged a lot about its chancel composition and terrestrial features, Saturn gave away wonderful secrets of its exquisite rings.

The NASA spacecraft, Juno, which has been orbiting the gas giant since July 2016, may provide important data and explanation to the puzzle. Nichols says, “Jupiter acts as an analogy for exoplanets, for brown dwarfs, for pulsars — a whole variety of astrophysical objects that we can’t get to,” he says. “So if we can understand Jupiter’s magnetic field then we can understand these whole different classes of objects.” Humanity is certainly fortunate to have a prototype of an exoplanet near its home. 

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