The nature of lightning on Jupiter has always remained a mystery to scientists. However, thanks to the work of the Juno space probe, astronomers have finally figured out that lightning on the gas giant has much more in common with the earthly than previously thought. However, this does not make them any less strange.
Data provided by NASA's Juno spacecraft showed that lightning strikes on Jupiter can occur in the megahertz range, and not just in the kilohertz range, as previously observed. Based on the information received, the two scientific groups prepared their reports.
“Before the Juno mission, lightning strikes on Jupiter were recorded by devices either visually or in the kilohertz range of radio waves, but not in the megahertz range, which is typical for lightning on Earth. Many theories have been proposed that could explain this phenomenon, but none of them offered a definite answer, said Shannon Brown, a scientist at NASA's Jet Propulsion Laboratory.
In the harsh atmosphere of Jupiter, numerous storms are quite common. Scientists have long assumed that lightning in this case may also be there. This phenomenon was confirmed when the Voyager 1 space probe flew past Jupiter in March 1979, which showed thunderstorm activity on the gas giant. Subsequently, this activity was confirmed using the Voyager-2, Galileo and Cassini vehicles. The low frequency signals discovered by the first Voyager were informally nicknamed "whistle" because they resembled the descending sound of a whistle.
However, scientists all this time were interested in why lightning on Jupiter differ from similar phenomena on Earth and generate radio waves only in a limited frequency range. Several theories have been proposed to address the issue, but none have come close to the answer.
Since 2016, "Juno" has recorded 377 discharges using a radio wave radiometer capable of capturing wide-range electromagnetic waves as part of eight complete orbits of the planet. These flares generated radio waves in the megahertz and gigahertz bands, which showed them to be similar to lightning on Earth.
“It seems to us that we managed to determine the presence of radio waves in the megahertz and gigahertz ranges due to the fact that the space probe“Juno”was closest to all others to these lightnings. In addition, we specifically monitored radio frequencies that could break through Jupiter's ionosphere,”says Brown.
Scientists also report that on Jupiter, almost all thunderstorm activity is localized at the poles, while on Earth, lightning occurs more often at the equator. The latter is explained by the fact that tropical and equatorial latitudes on Earth receive more heat from the Sun than regions of temperate and polar climates. As a result, warm, moist air rises through convection, causing frequent thunderstorms.
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Jupiter receives 25 times less heat from the Sun than the Earth, but at the same time emits a huge amount of internal thermal energy. At the equator, a balance is created between the latter and the radiation coming from outside, which prevents convection. At the poles, warm gases rise freely, creating conditions for heavy thunderstorms. At the same time, it is noted that most often lightning occurs precisely in the northern hemisphere of the gas giant. As part of further research on the planet, scientists want to find an explanation for this.
A second scientific article, published by researchers from the Czech Academy of Sciences, states that Jupiter's lightning has more in common with Earth's. Having recorded and analyzed more than 1600 radio signals (Voyager 1 managed to collect data on only 167), scientists found out that at the peak of lightning activity on Jupiter, they strike at a frequency of 4 strikes per second, which is similar to those observed on Earth. The Voyager 1 data, due to the small sample, showed only one hit in a few seconds.
Together, both studies provide the most detailed picture of thunderstorm activity on Jupiter and provide scientists with important clues for understanding the complex dynamic processes taking place inside the planet's dense thunderclouds.
"This data will help us better understand the composition and circulation of energy flows that flow on Jupiter," said Brown.
Recall that the Juno probe was launched in August 2011. It entered the orbit of Jupiter in 2016, and in July 2017, the device for the first time took pictures of the Great and Small red spots of the planet.
More recently, it became known that NASA has extended the work of the Juno mission to explore Jupiter until 2021. It is noted that the probe will be able to make 23 more flights through the upper atmosphere of Jupiter and perform many tasks.
Nikolay Khizhnyak