Cassini sheds light on cosmic particle accelerators

Feb 20, 2013
This artist's impression by the European Space Agency shows NASA's Cassini spacecraft exploring the magnetic environment of Saturn. Credit: ESA

(Phys.org)—During a chance encounter with what appears to be an unusually strong blast of solar wind at Saturn, NASA's Cassini spacecraft detected particles being accelerated to ultra-high energies. This is similar to the acceleration that takes place around distant supernovas.

Since we can't travel out to the far-off stellar explosions right now, the shockwave that forms from the flow of solar wind around Saturn's magnetic field provides a rare laboratory for scientists with the —a partnership involving NASA, the and the Italian Space Agency—to observe this phenomenon up-close. The findings, published this week in the journal Nature Physics, confirm that certain kinds of shocks can become considerably more effective electron accelerators than previously thought.

are commonplace in the universe, for example in the aftermath of a as debris accelerate outward in a supernova remnant, or when the flow of particles from the sun - the solar wind - impinges on the magnetic field of a planet to form a bow shock. Under certain magnetic field orientations and depending on the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. These may be the dominant source of cosmic rays, high-energy particles that pervade our galaxy.

This illustration shows "quasi-parallel" (top) and "quasi-perpendicular" (bottom) magnetic field conditions at a planetary bow shock. Bow shocks are shockwaves created when the solar wind blows on a planet's magnetic field. Credit: ESA

Scientists are particularly interested in "quasi-parallel" shocks, where the magnetic field and the "forward"-facing direction of the shock are almost aligned, as may be found in supernova remnants. The new study, led by Adam Masters of the Institute of Space and Astronautical Science, Sagamihara, Japan, describes the first detection of significant acceleration of electrons in a quasi-parallel shock at Saturn, coinciding with what may be the strongest shock ever encountered at the ringed planet.

"Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own solar system, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely," said Masters.

Explore further: Scientists find meteoritic evidence of Mars water reservoir

Related Stories

Voyager observes magnetic field fluctuations in heliosheath

Oct 29, 2012

As they near the outer reaches of the solar system, for the past several years the two Voyager spacecraft have been sending back observations that challenge scientists' views of the physics at the edge of the heliosphere, ...

Cosmic particle accelerators get things going

Nov 17, 2011

(PhysOrg.com) -- ESA's Cluster satellites have discovered that cosmic particle accelerators are more efficient than previously thought. The discovery has revealed the initial stages of acceleration for the ...

Exploding stars and stripes

Mar 24, 2011

The discovery of a pattern of X-ray "stripes" in the remains of an exploded star may provide the first direct evidence that a cosmic event can accelerate particles to energies a hundred times higher than achieved ...

ACE, workhorse of NASA's heliophysics fleet, is 15

Aug 30, 2012

(Phys.org)—The Advanced Composition Explorer (ACE) is Earth's vanguard. Orbiting around a point 900,000 miles away between the Earth and our sun, this satellite is ever vigilant, recording the combination ...

Recommended for you

Politics no problem, say US and Russian spacefarers

12 hours ago

US-Russian ties may have returned to Cold War levels, but an astronaut and a cosmonaut gearing up for the longest flight on the International Space Station said Thursday politics would not disrupt their work ...

User comments : 18

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
1 / 5 (8) Feb 20, 2013
What they insist on describing as a "bow shock", suggesting it's a purely mechanical phenomenon, is in fact a plasma double layer. And from years of empirical data of plasma research, we know that these double layers DO in fact accelerate particles to relativistic speeds.

These may be the dominant source of cosmic rays, high-energy particles that pervade our galaxy.

They are correct to presume that high energy particles originate in plasma double layers. Hannes Alfven suggested the double layer as a distinct celestial object.
cantdrive85
1 / 5 (6) Feb 20, 2013
Sources of cosmic rays were predicted by Alfvén in 1986 in an IEEE publication and NASA Conference Publication 2469, "Double Layers in Astrophysics." He explains:

"Since the time of Langmuir, we know that a double layer is a plasma formation by which a plasma — in the physical meaning of this word — protects itself from the environment. It is analogous to a cell wall by which a plasma — in the biological meaning of this word — protects itself from the environment. If an electric discharge is produced between a cathode and an anode there is a double layer, called a cathode sheath, produced near the cathode that accelerates electrons which carry a current through the plasma. A positive space charge separates the cathode sheath from the plasma. Similarly, a double layer is set up near the anode, protecting the plasma from this electrode. Again, a space charge constitutes the border between the double layer and the plasma. All these double layers carry electric currents."

barakn
5 / 5 (3) Feb 20, 2013
Ok, so I'm confused. Which part of the Saturn magnetic field is the cathode and which is the anode?
cantdrive85
1 / 5 (3) Feb 20, 2013
The anode is Saturn itself, the cathode is a "virtual cathode" represented by the outer layer of Saturn's EM field.
katesisco
1 / 5 (2) Feb 20, 2013
well then, did the entry through the Earth magnetosphere accelerate the meteorite over Russia?
cantdrive85
1 / 5 (7) Feb 20, 2013
Being a meteorite is not a particle, no it was not accelerated to relativistic speeds by the Earth's DL's. However, the meteorite which has it's own charge compared to the Earth's will create plasma sheath around itself to protect itself from the surrounding environment. As it approached lower levels of Earth's plasma sheath the voltage between the object and the layer and the object will begin to discharge visibly. It will begin as a "glow discharge" and as the voltage increased it will then jump to arc mode, and the object would become an electrode at the focus of upper-atmospheric charge. At which point it will ablate material or as in this case, the difference is great enough to cause an explosive event, much of the explosive energy coming from the energy stored in the electric and magnetic fields of the DL's along with the kinetic energy and chemical energy.
Q-Star
3.4 / 5 (5) Feb 20, 2013
Being a meteorite is not a particle, no it was not accelerated to relativistic speeds by the Earth's DL's. However, the meteorite which has it's own charge compared to the Earth's will create plasma sheath around itself to protect itself from the surrounding environment. As it approached lower levels of Earth's plasma sheath the voltage between the object and the layer and the object will begin to discharge visibly. It will begin as a "glow discharge" and as the voltage increased it will then jump to arc mode, and the object would become an electrode at the focus of upper-atmospheric charge. At which point it will ablate material or as in this case, the difference is great enough to cause an explosive event, much of the explosive energy coming from the energy stored in the electric and magnetic fields of the DL's along with the kinetic energy and chemical energy.


I see ya have been studying Zephyr,,, ya left out the electron-ducks paddling through the plasma part though.
cantdrive85
1 / 5 (5) Feb 20, 2013
I'm not familiar with Zephyr, and I don't recall Alfven discussing "electron ducks" during his Nobel speech. Please enlighten so I don't confuse this as being some sort of strawman argument.
ValeriaT
1 / 5 (5) Feb 20, 2013
You should know, that Q-Star uses nothing but strawman "arguments" here. He's a sockpuppet of "lite" voting troll.
Q-Star
3.4 / 5 (5) Feb 20, 2013
You should know, that Q-Star uses nothing but strawman arguments here.


So ya think he is wrong about the plasma meteor model of recent evens? But, Zeph, the Straw-man Model of the universe is much more defensible than the Plasma-man Model.

Though the Electron-duck Model is a pretty good one too, I don't think it will work well with meteors.
Q-Star
3.4 / 5 (5) Feb 20, 2013
He's a sockpuppet of "lite" voting troll.


Sock-puppet? Me? That is a good one coming from Zephyr, Natello, Yash17 and ValeriaT. (And the other (two) guy(s) who I can't think of right now.)

By the By: Why are so many people obsessed with lite? It only points out what is really important to ya. He gives me one's too, but it's no big deal. So what?
ValeriaT
1 / 5 (3) Feb 20, 2013
Why are so many people obsessed with lite
Many people are downvoted with lite, maybe this is the reason. What do think?
Straw-man Model of the universe is much more defensible than the Plasma-man Model
This is just a void twaddling. You needn't to have any qualification for saying it, physical the less. Every imbecile could say the same stuffs whole day without any mental effort. I'm not saying, you're imbecile - but I've no observational evidence for it.
Q-Star
2 / 5 (4) Feb 20, 2013
Why are so many people obsessed with lite
Many people are downvoted with lite, maybe this is the reason. What do think?


I think ya are exactly right. That's why I said this obsession only points out what seems to be most important to people. I for one don't care about the votes. I give fives when I agree with a poster. And ones to people who are just writing a lot without caring much what they right.

I rarely vote for you. I've even taken up for you in comments to other posters on occasion. I vote you a five, as often as I vote you a one.

I'm actually quite fond of you, I rarely understand you, but I do read everything you post.
Gawad
5 / 5 (6) Feb 20, 2013
I'm actually quite fond of you, I rarely understand you, but I do read everything you post.


Holy Hell! At least don't encourage him! When he goes off on a tear he can start polluting threads with reams and reams of meaningless crackpot gobbledygook, and although I occasionally check some of it out for its entertainement value...jeeze...I'd never admit to reading all of it even if I did just so as not to encourage more of it. Please! It's not like it's THAT funny. Cold fusion and aether posts get old after the 25 567th time. Ya know?
Q-Star
2.3 / 5 (3) Feb 20, 2013
I'm actually quite fond of you, I rarely understand you, but I do read everything you post.


Holy Hell! At least don't encourage him! When he goes off on a tear he can start polluting threads with reams and reams of meaningless crackpot gobbledygook, and although I occasionally check some of it out for its entertainement value...jeeze...I'd never admit to reading all of it even if I did just so as not to encourage more of it. Please! It's not like it's THAT funny. Cold fusion and aether posts get old after the 25 567th time. Ya know?


Your admonishment is received (I vote ya a five for it), and I will try to be more considerate. (When I fail, try just scrolling past the gobbledegook, that works for me when I'm in a hurry.)
typicalguy
not rated yet Feb 20, 2013
Gotta love the Nobel prize comment. I didn't realize that was proof positive? If that's the case, I'm sure I can line up a lot of Nobel prize winners that disagree. You lose. GG NOOB
EyeNStein
1 / 5 (2) Feb 21, 2013
Is this the same phenomena which has been proposed to shield future spacecraft? Using relatively weak magnetic fields: The heavy ions and light electrons deflect differentiantially and form a strong electric field which forms the effective shield needed. The ions 'space charge' forms the anode and electon 'space charge' being the cathode of this protective shell.
katesisco
1 / 5 (2) Feb 21, 2013
Thanks for the comment cantdrive, I am thinking that the v small meteorite was wrapped in compressed gas which burnt off completely leading to the explosion. Would there have been detectable radiation?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.