For almost 40 years now, astronomers have been studying the mysterious x-ray aurora borealis on Jupiter. Their origin has finally been discovered, as the ESA reports today.
Until now, scientists knew from their colors that they were triggered by electrically charged particles, called ions, which crash into Jupiter’s atmosphere. Now we know how these ions get to the atmosphere. They would have a direct link with the spectacular ultraviolet storms called sub-auroral storms .
Zhonghua Yao, of the Institute of Geology and Geophysics at the Chinese Academy of Sciences in Beijing, found that the high latitude polar regions of Jupiter and Saturn should not normally emit substantial aurora . However, we know that auroras take place on Jupiter and can sometimes be different depending on the pole where they occur. These are the typical characteristics of a “closed ” magnetic field , where the magnetic field line exits the planet at one pole and reconnects with the planet at the other .
Zhonghua and his colleagues discovered that pulsating x-ray auroras could be linked to closed magnetic fields. These are generated inside Jupiter and then stretch for millions of kilometers in space before turning around . Using data from ESA’s XMM-Newton telescope and NASA’s Juno probe that arrived in orbit from Jupiter in 2016 , scientists found that ions could “surf” on electromagnetic waves in the magnetic field of Jupiter, up to the atmosphere .
Pulsed X-ray auroras are caused by fluctuations in Jupiter’s magnetic field
As the planet rotates, it causes its magnetic field, which is about 20,000 times stronger than that of the Earth. This one is directly struck by the particles of the solar wind and compressed. These compressions heat the ions that are trapped in Jupiter’s magnetic field. This triggers a phenomenon called cyclotron ionic electromagnetic waves (EMIC) .
Guided by the field, the ions “ride” the EMIC wave across millions of kilometers, eventually crashing into the planet’s atmosphere and triggering the aurora of x-rays . The process behind the x-ray aurora borealis on Jupiter is not believed to be unique. Indeed, it would even occur in many other parts of the Universe.
Source: ESA
