auroras on jupiter

Magnetospheres: How Do They Work?

The sun, Earth, and many other planets are surrounded by giant magnetic bubbles.

Space may seem empty, but it’s actually a dynamic place, dominated by invisible forces, including those created by magnetic fields.  Magnetospheres – the areas around planets and stars dominated by their magnetic fields – are found throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are mostly spewed out by the sun, but can also come from interstellar space. Along with atmospheres, they help protect the planets’ surfaces from this harmful radiation.

It’s possible that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, so finding magnetospheres around other planets is a big step toward determining if they could support life.

But not all magnetospheres are created equal – even in our own backyard, not all planets in our solar system have a magnetic field, and the ones we have observed are all surprisingly different.

Earth’s magnetosphere is created by the constantly moving molten metal inside Earth. This invisible “force field” around our planet has an ice cream cone-like shape, with a rounded front and a long, trailing tail that faces away from the sun. The magnetosphere is shaped that way because of the constant pressure from the solar wind and magnetic fields on the sun-facing side.

Earth’s magnetosphere deflects most charged particles away from our planet – but some do become trapped in the magnetic field and create auroras when they rain down into the atmosphere.

We have several missions that study Earth’s magnetosphere – including the Magnetospheric Multiscale mission, Van Allen Probes, and Time History of Events and Macroscale Interactions during Substorms (also known as THEMIS) – along with a host of other satellites that study other aspects of the sun-Earth connection.

Mercury, with a substantial iron-rich core, has a magnetic field that is only about 1% as strong as Earth’s. It is thought that the planet’s magnetosphere is stifled by the intense solar wind, limiting its strength, although even without this effect, it still would not be as strong as Earth’s. The MESSENGER satellite orbited Mercury from 2011 to 2015, helping us understand our tiny terrestrial neighbor.

After the sun, Jupiter has by far the biggest magnetosphere in our solar system – it stretches about 12 million miles from east to west, almost 15 times the width of the sun. (Earth’s, on the other hand, could easily fit inside the sun.) Jupiter does not have a molten metal core like Earth; instead, its magnetic field is created by a core of compressed liquid metallic hydrogen.

One of Jupiter’s moons, Io, has intense volcanic activity that spews particles into Jupiter’s magnetosphere. These particles create intense radiation belts and the large auroras around Jupiter’s poles.

Ganymede, Jupiter’s largest moon, also has its own magnetic field and magnetosphere – making it the only moon with one. Its weak field, nestled in Jupiter’s enormous shell, scarcely ruffles the planet’s magnetic field.

Our Juno mission orbits inside the Jovian magnetosphere sending back observations so we can better understand this region. Previous observations have been received from Pioneers 10 and 11, Voyagers 1 and 2, Ulysses, Galileo and Cassini in their flybys and orbits around Jupiter.

Saturn’s moon Enceladus transforms the shape of its magnetosphere. Active geysers on the moon’s south pole eject oxygen and water molecules into the space around the planet. These particles, much like Io’s volcanic emissions at Jupiter, generate the auroras around the planet’s poles. Our Cassini mission studies Saturn’s magnetic field and auroras, as well as its moon Enceladus.

Uranus’ magnetosphere wasn’t discovered until 1986 when data from Voyager 2’s flyby revealed weak, variable radio emissions. Uranus’ magnetic field and rotation axis are out of alignment by 59 degrees, unlike Earth’s, whose magnetic field and rotation axis differ by only 11 degrees. On top of that, the magnetic field axis does not go through the center of the planet, so the strength of the magnetic field varies dramatically across the surface. This misalignment also means that Uranus’ magnetotail – the part of the magnetosphere that trails away from the sun – is twisted into a long corkscrew.

Neptune’s magnetosphere is also tilted from its rotation axis, but only by 47. Just like on Uranus, Neptune’s magnetic field strength varies across the planet. This also means that auroras can be seen away from the planet’s poles – not just at high latitudes, like on Earth, Jupiter and Saturn.

Does Every Planet Have a Magnetosphere?

Neither Venus nor Mars have global magnetic fields, although the interaction of the solar wind with their atmospheres does produce what scientists call an “induced magnetosphere.” Around these planets, the atmosphere deflects the solar wind particles, causing the solar wind’s magnetic field to wrap around the planet in a shape similar to Earth’s magnetosphere.

What About Beyond Our Solar System?

Outside of our solar system, auroras, which indicate the presence of a magnetosphere, have been spotted on brown dwarfs – objects that are bigger than planets but smaller than stars.

There’s also evidence to suggest that some giant exoplanets have magnetospheres. As scientists now believe that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, finding magnetospheres around exoplanets is a big step in finding habitable worlds.  

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Milky Way Rising and Aurora on a May Night by Alan Dyer
Via Flickr:
The arch of the northern summer Milky Way across the Alberta prairie sky on a spring night, with the glow of aurora to the north at left. At right are Saturn and Antares in Scorpius low in the south, and bright Jupiter at far right, with Spica to the left of Jupiter and Arcturus above at top right. The Summer Triangle stars are at centre straddling the Milky Way…Shot from home with the Rokinon 14mm SP lens at f/2.5 and Canon 6D at ISO 6400 for a stitch of 9 exposures, each 30 seconds. Stitched with PTGui. This was about 1 am May 16, just before local moonrise.

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Surprisingly erratic X-ray auroras discovered at Jupiter

ESA and NASA space telescopes have revealed that, unlike Earth’s polar lights, the intense auroras seen at Jupiter’s poles unexpectedly behave independently of one another.

Auroras have been seen in many places, from planets and moons to stars, brown dwarfs and a variety of other cosmic bodies. These beautiful displays are caused by streams of electrically charged atomic particles – electrons and ions – colliding with the atmospheric layers surrounding a planet, moon or star. Earth’s polar lights tend to mirror one another: when they brighten at the North pole, they generally brighten at the South pole, too.

The same was expected of auroras elsewhere, but a new study, published today in Nature Astronomy, reveals that those at the gas giant Jupiter are much less coordinated.

The study used ESA’s XMM-Newton and NASA’s Chandra X-ray space observatories to observe the high-energy X-rays produced by the auroras at Jupiter’s poles. While the southern auroras were found to pulse consistently every 11 minutes, those at the planet’s north pole flared chaotically.

“These auroras don’t seem to act in unison like those that we’re often familiar with here on Earth,” says lead author William Dunn of University College London’s Mullard Space Science Laboratory, UK, and Harvard-Smithsonian Center for Astrophysics, USA.

“We thought the activity would be coordinated through Jupiter’s magnetic field, but the behaviour we found is really puzzling.

“It’s stranger still considering that Saturn – another gas giant planet – doesn’t produce any X-ray auroras that we can detect, so this throws up a couple of questions that we’re currently unsure how to answer.

“Firstly, how does Jupiter produce bright and energetic X-ray auroras at all when its neighbour doesn’t, and secondly, how does it do so independently at each pole?”

With the data at hand, William and colleagues identified and mapped X-ray hot spots at Jupiter’s poles. Each hot spot covers an area half the size of Earth’s surface.

As well as raising questions about how auroras are produced throughout the cosmos, Jupiter’s independently pulsing auroras suggest that there is far more to understand about how the planet itself produces some of its most energetic emissions.

Jupiter’s magnetic influence is colossal; the region of space over which the Jovian magnetic field dominates – the magnetosphere – is some 40 times larger than Earth’s, and filled with high-energy plasma. In the outer edges of this region, charged particles ultimately from volcanic eruptions on Jupiter’s moon, Io, interact with the magnetic boundary between the magnetosphere and interplanetary space. These interactions create intense phenomena, including auroras.


“Charged particles have to hit Jupiter’s atmosphere at exceptionally fast speeds in order to generate the X-ray pulses that we’ve seen. We don’t yet understand what processes cause this, but these observations tell us that they act independently in the northern and southern hemispheres,” adds Licia Ray, from Lancaster University, UK, and a co-author.

The asymmetry in Jupiter’s northern and southern lights also suggests that many cosmic bodies that are known to experience auroras – exoplanets, neutron stars, brown dwarfs and other rapidly-rotating bodies – might produce a very different aurora at each pole.

Further studies of Jupiter’s auroras will help to form a clearer picture of the phenomena produced at Jupiter; auroral observing campaigns are planned for the next two years, with X-ray monitoring by XMM-Newton and Chandra and simultaneous observations from NASA’s Juno, a spacecraft that started orbiting Jupiter in mid-2016.

ESA’s Juice will arrive at the planet by 2029, to investigate Jupiter’s atmosphere and magnetosphere. It, too, will observe the auroras and in particular the effect on them of the Galilean moons.

“This is a breakthrough finding, and it couldn’t have been done without ESA’s XMM-Newton,” adds Norbert Schartel, ESA project scientist for XMM-Newton.

“The space observatory was critical to this study, providing detailed data at a high spectral resolution such that the team could explore the vibrant colours of the auroras and figure out details about the particles involved: if they’re moving fast, whether they’re an oxygen or sulphur ion, and so on.

“Coordinated observations like these, with telescopes such as XMM-Newton, Chandra and Juno working together, are key in exploring and further understanding environments and phenomena across the Universe, and the processes that produce them.”

Extreme Jupiter weather and magnetic fields

New observations about the extreme conditions of Jupiter’s weather and magnetic fields by University of Leicester astronomers have contributed to the revelations and insights coming from the first close passes of Jupiter by NASA’s Juno mission, announced on May 25.

The astronomers from the University’s Department of Physics and Astronomy, led by the UK science lead for the Juno mission, have led three papers and contributed to four papers in Geophysical Research Letters, a journal of the American Geophysical Union, that support the first in-depth science results from Juno published in the journal Science.

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Hubble is capturing stunning photos of Jupiter’s giant auroras    

The vivid glows are created when charged particles enter the gas giant’s atmosphere near its magnetic poles; the collision with atoms and molecules in the atmosphere produce the light. While on Earth the biggest auroras are caused by solar storms — when high energy particles ejected from the Sun rain down on our planet — auroras on Jupiter are also caused by the charged particles ejected by other sources, like the planet’s orbiting moon Io. The auroras also never cease and are huge, covering areas bigger than the Earth itself.

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Jupiter’s North Pole Unlike Anything Encountered in Solar System


NASA’s Juno spacecraft has sent back the first-ever images of Jupiter’s north pole, taken during the spacecraft’s first flyby of the planet with its instruments switched on. The images show storm systems and weather activity unlike anything previously seen on any of our solar system’s gas-giant planets.

Juno successfully executed the first of 36 orbital flybys on Aug. 27 when the spacecraft came about 2,500 miles (4,200 kilometers) above Jupiter’s swirling clouds. The download of six megabytes of data collected during the six-hour transit, from above Jupiter’s north pole to below its south pole, took one-and-a-half days. While analysis of this first data collection is ongoing, some unique discoveries have already made themselves visible.

“First glimpse of Jupiter’s north pole, and it looks like nothing we have seen or imagined before,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “It’s bluer in color up there than other parts of the planet, and there are a lot of storms. There is no sign of the latitudinal bands or zone and belts that we are used to – this image is hardly recognizable as Jupiter. We’re seeing signs that the clouds have shadows, possibly indicating that the clouds are at a higher altitude than other features.”

One of the most notable findings of these first-ever pictures of Jupiter’s north and south poles is something that the JunoCam imager did not see.

“Saturn has a hexagon at the north pole,” said Bolton. “There is nothing on Jupiter that anywhere near resembles that. The largest planet in our solar system is truly unique. We have 36 more flybys to study just how unique it really is.”

Along with JunoCam snapping pictures during the flyby, all eight of Juno’s science instruments were energized and collecting data. The Jovian Infrared Auroral Mapper (JI-RAM), supplied by the Italian Space Agency, acquired some remarkable images of Jupiter at its north and south polar regions in infrared wavelengths.

“JIRAM is getting under Jupiter’s skin, giving us our first infrared close-ups of the planet,” said Alberto Adriani, JIRAM co-investigator from Istituto di Astrofisica e Planetologia Spaziali, Rome. “These first infrared views of Jupiter’s north and south poles are revealing warm and hot spots that have never been seen before. And while we knew that the first ever infrared views of Jupiter’s south pole could reveal the planet’s southern aurora, we were amazed to see it for the first time. No other instruments, both from Earth or space, have been able to see the southern aurora. Now, with JIRAM, we see that it appears to be very bright and well structured. The high level of detail in the images will tell us more about the aurora’s morphology and dynamics.”

Among the more unique data sets collected by Juno during its first scientific sweep by Jupiter was that acquired by the mission’s Radio/Plasma Wave Experiment (Waves), which recorded ghostly- sounding transmissions emanating from above the planet. These radio emissions from Jupiter have been known about since the 1950s but had never been analyzed from such a close vantage point.

“Jupiter is talking to us in a way only gas-giant worlds can,” said Bill Kurth, co-investigator for the Waves instrument from the University of Iowa, Iowa City. “Waves detected the signature emissions of the energetic particles that generate the massive auroras which encircle Jupiter’s north pole. These emissions are the strongest in the solar system. Now we are going to try to figure out where the electrons come from that are generating them.”

The Juno spacecraft launched on Aug. 5, 2011, from Cape Canaveral, Florida and arrived at Jupiter on July 4, 2016. JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. Caltech in Pasadena, California, manages JPL for NASA.

IMAGE 1….As NASA’s Juno spacecraft closed in on Jupiter for its Aug. 27, 2016 pass, its view grew sharper and fine details in the north polar region became increasingly visible.
The JunoCam instrument obtained this view on August 27, about two hours before closest approach, when the spacecraft was 120,000 miles (195,000 kilometers) away from the giant planet (i.e., for Jupiter’s center).
Unlike the equatorial region’s familiar structure of belts and zones, the poles are mottled with rotating storms of various sizes, similar to giant versions of terrestrial hurricanes. Jupiter’s poles have not been seen from this perspective since the Pioneer 11 spacecraft flew by the planet in 1974.

IMAGE 2….Storm systems and weather activity unlike anything encountered in the solar system are on view in these color images of Jupiter’s north polar region from NASA’s Juno spacecraft.
Two versions of the image have been contrast-enhanced differently to bring out detail near the dark terminator and near the bright limb.
The JunoCam instrument took the images to create this color view on August 27, when the spacecraft was about 48,000 miles (78,000 kilometers) above the polar cloud tops.
A wavy boundary is visible halfway between the grayish region at left (closer to the pole and the nightside shadow) and the lighter-colored area on the right. The wavy appearance of the boundary represents a Rossby wave – a north-south meandering of a predominantly east-west flow in an atmospheric jet. This may be caused by a difference in temperature between air to the north and south of this boundary, as is often the case with such waves in Earth’s atmosphere.
The polar region is filled with a variety of discrete atmospheric features. Some of these are ovals, but the larger and brighter features have a “pinwheel” shape reminiscent of the shape of terrestrial hurricanes. Tracking the motion and evolution of these features across multiple orbits will provide clues about the dynamics of the Jovian atmosphere.
This image also provides the first example of cloud shadowing on Jupiter: near the top of the image, a high cloud feature is seen past the normal boundary between day and night, illuminated above the cloud deck below.
While subtle color differences are visible in the image, some of these are likely the result of scattered light within the JunoCam optics. Work is ongoing to characterize these effects.

IMAGE 3….This image from NASA’s Juno spacecraft provides a never-before-seen perspective on Jupiter’s south pole.
The JunoCam instrument acquired the view on August 27, 2016, when the spacecraft was about 58,700 miles (94,500 kilometers) above the polar region. At this point, the spacecraft was about an hour past its closest approach, and fine detail in the south polar region is clearly resolved.
Unlike the equatorial region’s familiar structure of belts and zones, the poles are mottled by clockwise and counterclockwise rotating storms of various sizes, similar to giant versions of terrestrial hurricanes. The south pole has never been seen from this viewpoint, although the Cassini spacecraft was able to observe most of the polar region at highly oblique angles as it flew past Jupiter on its way to Saturn in 2000

IMAGE 4….This infrared image gives an unprecedented view of the southern aurora of Jupiter, as captured by NASA’s Juno spacecraft on August 27, 2016.
The planet’s southern aurora can hardly be seen from Earth due to our home planet’s position in respect to Jupiter’s south pole. Juno’s unique polar orbit provides the first opportunity to observe this region of the gas-giant planet in detail.
Juno’s Jovian Infrared Auroral Mapper (JIRAM) camera acquired the view at wavelengths ranging from 3.3 to 3.6 microns – the wavelengths of light emitted by excited hydrogen ions in the polar regions. The view is a mosaic of three images taken just minutes apart from each other, about four hours after the perijove pass while the spacecraft was moving away from Jupiter.

IMAGE 5….This montage of 10 JunoCam images shows Jupiter growing and shrinking in apparent size before and after NASA’s Juno spacecraft made its closest approach on August 27, 2016, at 12:50 UTC.
The images are spaced about 10 hours apart, one Jupiter day, so the Great Red Spot is always in roughly the same place. The small black spots visible on the planet in some of the images are shadows of the large Galilean moons.
The images in the top row were taken during the inbound leg of the orbit, beginning on August 25 at 13:15 UTC when Juno was 1.4 million miles (2.3 million kilometers) away from Jupiter, and continuing to August 27 at 04:45 UTC when the spacecraft was 430,000 miles (700,000 kilometers) away. The images in the bottom row were obtained during the outbound leg of the orbit. They begin on August 28 at 00:45 UTC when Juno was 750,000 miles (920,000 kilometers) away and continue to August 29 at 16:45 UTC when the spacecraft was 1.6 million miles (2.5 million kilometers) away.

IMAGE 6….This image provides a close-up view of Jupiter’s southern hemisphere, as seen by NASA’s Juno spacecraft on August 27, 2016. The JunoCam instrument captured this image with its red spectral filter when the spacecraft was about 23,600 miles (38,000 kilometers) above the cloud tops.
The image covers an area from close to the south pole to 20 degrees south of the equator, centered on a longitude at about 140 degrees west. The transition between the banded structures near the equator and the more chaotic polar region (south of about 65 degrees south latitude) can be clearly seen.
The smaller version at right of this image shows the same view with a latitude/longitude grid overlaid.
This image has been processed to remove shading effects near the terminator – the dividing line between day and night – caused by Juno’s orbit.