The wind was unable to trap hot gases at the gas giant's poles, allowing the auroras to heat its entire atmosphere.
Jupiter is more than five times farther from the Sun than it is from Earth, and it receives much less solar radiation. Calculations show that the temperature in the upper atmosphere of the gas giant should remain below minus 70 ° C. However, real observations show something completely different, and scientists have long been looking for an energy source that heats the atmosphere above 400 ° C.
The main contenders for the role of such a source are the auroras. Their participation in the heating of the planet's upper atmosphere was recently confirmed by observations of the Juno and Hisaki probes, as well as instruments of the Keck ground observatory. This is discussed in a new article published in the journal Nature.
The planet's magnetic field deflects most of the charged particles arriving from the Sun. However, some of them fall into "funnels" at the poles and rush downward, colliding with atoms in the upper atmosphere. Excited atoms lose energy again, emitting and creating flashes of aurora. Due to the strong magnetic field of Jupiter, as well as the influence of its satellites, auroras almost never subside and are considered the most powerful in the solar system.
However, modeling demonstrates that the gases heated by them, rushing from the poles towards the equator, should be restrained by winds directed along the parallels of the planet, arising from its rapid rotation. As a result, hot gases are trapped in the region of the poles and cannot so noticeably heat the rest of the atmosphere. But new observations have shown that the westerly wind is far from so strong in comparison with the intense equatorial currents.
Using the Keck II telescope's infrared spectrometer, astronomers tracked the transfer of heat from the poles to the equator itself. Previously, it was not possible to notice this due to the low resolution. Now it has been brought to two degrees of latitude and altitude. These images showed that temperatures near Jupiter's poles are nowhere near as high as they would be if hot air was trapped in these areas. When moving towards the equator, the temperature drops rather smoothly.
Keck II's observations were supported by the Japanese Hisaki probe. While in near-Earth orbit, he traced the magnetosphere of Jupiter at the same time periods in which the ground-based telescope recorded heat fluxes. At the same time, the Juno probe working near Jupiter filmed auroras near, collecting additional data on their dynamics. All this made it possible to draw up a detailed picture of the heating of the atmosphere of the gas giant and confirm the hypothesis about the participation of auroras in this.