Jupiter’s strange x-ray source revealed

The purple color in this image shows X-ray emission from Jupiter’s northern lights, which were discovered by NASA’s Chandra Space Telescope in 2007. They are overlaid on images of Jupiter captured by NASA’s Hubble Space Telescope. Jupiter is the only gas giant planet where scientists have found X-ray aurors. Sources: (X-ray) NASA / CXC / SwRI / R. Gladstone et al.; (Optics) NASA / ESA / Hubble Heritage (AURA / STScI)

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A riddle about the intense northern and southern lights of the gas giant has been deciphered.

Planetary astronomers combined measurements from NASA’s Juno spacecraft orbiting Jupiter with data from ESA’s orbiting XMM Newtonian mission to solve a 40-year-old mystery about the origin of Jupiter’s unusual X-ray Aurors. For the first time they saw the whole mechanism at work: the electrically charged atoms or ions, which are responsible for X-rays, “travel” electromagnetic waves in Jupiter’s magnetic field down into the gas giant’s atmosphere.

A paper on this research was published in the journal on July 9, 2021. released Scientific progress.

The northern lights have been found on seven planets in our solar system. Some of these light shows are visible to the human eye; others produce wavelengths of light that we can only see with special telescopes. Shorter wavelengths require more energy to produce. Jupiter has the strongest polar lights in the solar system and is the only one

Planetary astronomers have been intrigued by Jupiter’s X-ray auroral emissions since their discovery four decades ago because it was not immediately clear how the energy required to create them was generated. They knew that these surprising Jovian Northern and Southern Lights were triggered by ions crashing into Jupiter’s atmosphere. So far, however, scientists haven’t figured out how the ions responsible for the X-ray light show got into the atmosphere in the first place.

On Earth, auroras are usually only seen in the belt around the magnetic poles between latitudes 65 and 80 degrees. Beyond 80 degrees, the auroral rays disappear as magnetic field lines leave Earth and combine with the magnetic field in the solar wind, a constant stream of electrically charged particles ejected by the sun. These are called open field lines, and in traditional imagery, the polar regions at the high latitudes of Jupiter and Saturn are also not expected to emit substantial auroras.

However, Jupiter’s X-ray Aurors are different. They exist and pulse towards the polar belt of light, and those at the North Pole are often different from those at the South Pole. This is a characteristic of closed magnetic fields where the magnetic field lines leave the planet at one pole and reconnect with the planet at the other. All planets with magnetic fields have an open and closed field component.

Scientists studying the phenomenon turned to computer simulations and found that pulsating X-ray aurors could be connected to a closed magnetic field created inside Jupiter and then stretched millions of kilometers into space before expanding again. But how can you prove that the model is viable?

The study’s authors used data collected by Juno and XMM-Newton from July 16-17, 2017. Over a two-day period, XMM-Newton observed Jupiter continuously for 26 hours and saw X-ray aurorae pulsating every 27 minutes.

At the same time, Juno has traveled between 62 and 68 Jupiter radii (about 2.8 to 3 million miles, or 4.4 to 4.8 million kilometers) over the predawn area of ​​the planet. This is the region that, according to the team’s simulations, is important for triggering the pulse. So they searched the Juno data for magnetic processes occurring at the same speed.

They found that fluctuations in Jupiter’s magnetic field caused the X-ray aurors to pulse. The outer boundary of the magnetic field is struck and compressed directly by the solar wind particles. This compression heats ions trapped in Jupiter’s vast magnetic field, which is millions of miles from the planet’s atmosphere.

This triggers a phenomenon known as electromagnetic ionizing cyclotron (EMIC) waves, in which particles are directed along field lines. Guided by the field, the ions ride EMIC waves over millions of kilometers in space, eventually crashing into the planet’s atmosphere and triggering X-ray aurors.

“What we see in the Juno data is this beautiful series of events. We see compression taking place, we see triggered EMIC waves, we see ions, and then we see pulses of ions moving along field lines,” said William Dunn of the Mullard Space Science Laboratory, University College London, and co-author of the paper. “Then a few minutes later, XMM saw an x-ray burst.”

Once the missing part of the process is first identified, this opens up many possibilities where it can be examined later. On Jupiter, for example, the magnetic field is filled with sulfur and oxygen ions emitted by the volcano on the moon Io. On Saturn, the moon Enceladus emits water into space and fills Saturn’s magnetic field with water-group ions.

For more information on this discovery, see Scientists Solve Mystery of Jupiter’s Spectacular 40 Years of X-Ray Aurora.