Taking a spin on plasma space tornadoes with NASA observations

November 17, 2017 by Mara Johnson-Groh, NASA's Goddard Space Flight Center
This simulation of the boundary shows how areas of low density plasma, shown by blue, mix with areas of higher density plasma, red, forming turbulent tornadoes of plasma. Credit: NASA/Takuma Nakamura

Interplanetary space is hardly tranquil. High-energy charged particles from the Sun, as well as from beyond our solar system, constantly whizz by. These can damage satellites and endanger astronaut health—though, luckily for life on Earth, the planet is blanketed by a protective magnetic bubble created by its magnetic field. This bubble, called the magnetosphere, deflects most of the harmful high-energy particles.

Nevertheless, some sneak through—and at the forefront of figuring out just how this happens is NASA's Magnetospheric Multiscale mission, or MMS. New results show that tornado-like swirls of plasma create a boundary tumultuous enough to let slip into near Earth space.

MMS, launched in 2015, uses four identical spacecraft flying in a pyramid formation to take a three-dimensional look at the magnetic environment around Earth. The mission studies how particles transfer into the magnetosphere by focusing on the causes and effects of magnetic reconnection—an explosive event where lines cross, launching electrons and ions from the into the magnetosphere.

By combining observations from MMS with new 3-D computer simulations, scientists have been able to investigate the small-scale physics of what's happening at our magnetosphere's borders for the first time. The results, recently published in a paper in Nature Communications, are key for understanding how the solar wind sometimes enters Earth's magnetosphere, where it can interfere with satellites and GPS communications.

Kelvin-Helmholtz waves, with their classic surfer's wave shape, are found in nature wherever two fluids meet, such as in these clouds. Credit: Danny Ratcliffe

Inside the magnetosphere, the density of the space plasma—charged particles, like electrons and ions—is much lower than the plasma outside, where the solar wind prevails. The boundary, called the magnetopause, becomes unstable when the two different density regions move at different rates. Giant swirls, called Kelvin Helmholtz waves, form along the edge like crashing ocean waves. The once-smooth boundary becomes tangled and squeezed, forming plasma tornadoes, which act as portholes for the transportation of charged particles from the solar wind into the magnetosphere.

Kelvin Helmholtz waves are found across the universe wherever two materials of different density move past one another. They can be seen in cloud formations around Earth and have even been observed in other planetary atmospheres in our solar system.

Using large-scale computer simulations of this mixing, performed at the Oak Ridge National Laboratory in Oak Ridge, Tennessee, on the Titan supercomputer, and comparing them to observations MMS took while passing through such a region in space, scientists were able to show that the tornadoes were extremely efficient at transporting charged particles—much more so than previously thought. The comparisons between the simulations and observations allowed the scientists to measure the exact dimensions of the tornadoes. They found these tornadoes to be both large and small—ones reaching 9,300 miles spawned smaller tornadoes 60 to 90 miles wide and over 125 miles long.

MMS recently moved into a new orbit, flying on the far side of Earth, away from the Sun. Here too, it will continue to study magnetic reconnection, but focus instead on how energy and particles interact within Earth's , in the long trailing magnetotail. Understanding such fundamental processes in Earth's neighborhood helps improve our situational awareness of the space that surrounds us—crucial information as it becomes ever more filled with satellites and communications systems we depend on.

Explore further: Studying magnetic space explosions with NASA missions

More information: T. K. M. Nakamura et al. Turbulent mass transfer caused by vortex induced reconnection in collisionless magnetospheric plasmas, Nature Communications (2017). DOI: 10.1038/s41467-017-01579-0

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cantdrive85
1.4 / 5 (10) Nov 17, 2017
Kelvin-Helmholtz waves, with their classic surfer's wave shape, are found in nature wherever two fluids meet, such as in these clouds.

Once again, completely inappropriate physics are used to describe the interaction of two plasmas. These are not two electrically inert fluids but electrodynamic plasmas and must include electromagnetic forces as well. Rather than describing these interactions with fluid Kelvin-Helmholz instabilities one must describe this using plasma diocotron instabilities.
RogueParticle
4.3 / 5 (12) Nov 18, 2017
Rather than describing these interactions with fluid Kelvin-Helmholz instabilities one must describe this using plasma diocotron instabilities
So, Mr. Plasma, why don't you do that? Instead of just standing off to the side and sneering at others' attempts to explain what is observed, sit down and write a paper describing in detail exactly what happens at such boundaries: the physics, supported by deep mathematical analysis, and maybe throw in some computer simulations, for which you'll have to write the code.

We'd love to see the results...
Nik_2213
5 / 5 (7) Nov 18, 2017
"... one must describe this using plasma diocotron instabilities"

If so, please show working.
cantdrive85
1.4 / 5 (9) Nov 18, 2017
@RP
The double standard you are displaying is truly pathetic. You seem to think the "looks like a duck" use of K-H instabilities (qualitative at best) to describe these plasmas is fine and dandy for these researchers. Yet you are being critical of me pointing out there is a quantitative approach available by using relevant plasma physics to describe the interactions. Bravo!
cantdrive85
1.4 / 5 (9) Nov 18, 2017
"... one must describe this using plasma diocotron instabilities"


If so, please show working.

This paper suggests the use of EM-PIC codes to models diocotron instabilities.

https://www.googl...oALEqwtX

Here is another interesting page, scroll down half-way on page to see simulations, take a look at the cylindrical version which evolves into a hexagon.
https://www-m16.m...obAmeres
This is the cause of Saturn's polar hexagon, diocotron instabilities. When to correct plasma physics are used many of the mysteries of astrophysics will evaporate.
jonesdave
4.6 / 5 (9) Nov 18, 2017
The problem is, is that this isn't a diocotron instability. That applies for non-neutral plasmas. That isn't the case here. Hence why the KH model is used.

See: Physics of noneutral plasmas (section 6)
Davidson, R. C. (2001)
http://sutlib2.su...4383.pdf

Cited by 996. I believe Peratt says the same thing. As does that PU link.

CD will probably argue, but it is pointless, as. like Benni, he thinks that he can influence science by posting on here, trying to make himself look clever, but hasn't got the smarts to actually challenge the scientists that he claims are making these mistakes.
Captain Stumpy
4.3 / 5 (6) Nov 18, 2017
The problem is, is that this isn't a diocotron instability. That applies for non-neutral plasmas. That isn't the case here. Hence why the KH model is used
@Jones
yeah, it's been explained to him before by Q-Star (physics professor) and quite a few others

.

.

@idiot illiterate fanatical pseudoscience cult member cd
Once again, completely inappropriate physics are used to describe
if you could prove this, you would have written up a paper and published in a journal

problem is, as Jonesd, RogueP and Nik point out: even your own plasma physics engineers think you're wrong and an idiot

just FYI - Hasegawa studied Electrical Engineering and has published (repeatedly) in IEEE, the holy bible of the idiot eu cult

cantdrive85
1 / 5 (8) Nov 18, 2017
There goes jonesdumb again applying his ignorance regarding his inability to understand the difference between neutral and quasi-neutral. Space plasmas are quasi-neutral meaning on a whole there are equal quantities of ions-electrons but the in no way implies it is neutral. One need only look to the Van Allen beltss and the electric double layers that were measured in situ by spacecraft in orbit around Earth. And before spouting off about illegitimate claims of what Peratt saus you should point iut where he said these things.
jonesdave
4.3 / 5 (7) Nov 18, 2017
There goes jonesdumb again applying his ignorance regarding his inability to understand the difference between neutral and quasi-neutral. Space plasmas are quasi-neutral meaning on a whole there are equal quantities of ions-electrons but the in no way implies it is neutral. One need only look to the Van Allen beltss and the electric double layers that were measured in situ by spacecraft in orbit around Earth. And before spouting off about illegitimate claims of what Peratt saus you should point iut where he said these things.


Wrong. Look at equation 1.13 in Peratt's book. Over any reasonable distance in the plasma that they are measuring (with MMS) and modelling, ni - ne = 0.
As explained by a plasma physicist to another deluded EU cultist here:
http://www.intern...unt=3506

As Martin says, this is in a cometary magnetosphere, but the same principle applies in the Earth's magnetosphere. It is charge neutral.
gculpex
5 / 5 (3) Nov 18, 2017
Non-linear evolution of the diocotron instability in a pulsar electrosphere: 2D PIC simulations
J. Petri
(Submitted on 7 May 2009)
(abridged) The physics of the pulsar magnetosphere near the neutron star surface remains poorly constrained by observations. Nevertheless it is believed that large vacuum gaps exist in the magnetosphere, and a non-neutral plasma partially fills the neutron star surroundings to form an electrosphere.
The equatorial disk in this electrosphere is diocotron and magnetron unstable. To better assess the long term evolution of these instabilities, we study the behavior of the non-neutral plasma with help on particle simulations.
We designed a 2D electrostatic PIC code. In the diocotron regime, the equation of motion for particles obeys the electric drift approximation. The plasma is confined between two conducting walls. Moreover, in order to simulate a pair cascade in the gaps, we add a source term feeding the plasma with charged particles.
...
jonesdave
5 / 5 (4) Nov 18, 2017
^^^ Well said that man! So, under extreme circumstances we can consider the diocotron instability to be a possible reason for what is seen. No chance of me disagreeing with that! However, under the circumstances reported here, that would be a moronic thing to do. Yes? Glad you agree!
cantdrive85
1 / 5 (3) Nov 18, 2017
You have no compunction from lying, don't you jonesdumb. In Peratt's book 'Physics of the Plasma Universe', equation 1.13 does not state that at all [ I have a copy ;)]. I would copy and paste the equation to show your lie, but alas the simple text here will not allow. Anyways, he does say;
"Equations (1.13)-(1.15) are exactly the magnetron equations (c.f. 'Buneman Small Amplitude Theory" in Collins, Microwave Magnetrons), except that ni.=0 in a properly νacuum-ρumped
magnetron."
But we're not talking pumped magntrons are we?
We'll go over that section now;
1 .7.3 The Dίocotron Instabίlity
One of the outstanding problems in the propagation of electron beams along an axial magnetic field is the breakup of the beam into discrete vortex-like current bundles when a threshold determined by either the beam cuπent or distance of propagation is surpassed..."

TBC...
cantdrive85
1 / 5 (3) Nov 18, 2017
"...The phenomena observed, closely resembles that associated with the Kelvin—Helmholtz fluid dynamical shear instability, in
which vortices develop throughout a fluid when a critical velocity in the flow is exceeded, with a large increase in the resistance to flow [Chandrasekhar 1961] .
While structural changes in the azimuthal directi οηare observed in solid, annular, or sheet beams, it is with thin electron beams that the vortex phenomenon is most pronounced . Since thin
annular beams are easily produced and are capable of conducting intense currents, they have found widespread application in microwave generation and accelerators. Conversely, in many applications a cold beam is desired and the heating of the beam by the onset of instabilities is an undesired
property..."
cantdrive85
1 / 5 (4) Nov 18, 2017
"...The instability leading to the filamentatiοn of the beam is known as the "slipping steam" or "diοcοtron" and occurs when charge neutrality is not locally maintained, for example, when electrons and ions separate.
This mechanism was first introduced to explain auroral cuτtains (Figure 1 .21) by Alfνέn (1950). The diocotron instability as the cause of the auroral curtains is discussed in Section
2.9.8."
End of section, and a face plant for jonesdumb. The father of plasma physics proposed this as a cause of phenomena in near-Earth plasmas, doh!
Peratt also said this in section;
1.3 Regions of Αρρlίcabίlίty of Plasma Physics
"Neglecting lightning, planetary atmospheres and hydrospheres are the only domains in the uniνerse where a non-hydromagnetic treatment of fluid dynamic problems is jυstifιed."
Oooh! The final nail in that coffin, jonesdumb's knowledge is dead!
cantdrive85
1 / 5 (5) Nov 18, 2017
Being that the above paper is trying to explain how solar wind energy and particles get through the magnetosphere and intrrfere with our spacecraft and such, and we know that diocotron instabilities create electron beams via a vortex phenomena is there any need to continue denying the use of the proper plasma physics ILO the non-applicable fluid dynamics? That's what I thought...
jonesdave
5 / 5 (5) Nov 19, 2017
^^^^^ All of which is an irrelevance. What Alfven 'proposed' in the 50s is irrelevant. This is not the auroral zone, for a start. Furthermore, the researchers are modelling based on measurement from in-situ spacecraft. Which show that the non-neutral diocotron instability is not appropriate. Which is why they don't use it. If you think the data shows otherwise, then you need to point out where these plasma physicists have misinterpreted it. Which, of course, you cannot and will not do.
cantdrive85
1 / 5 (5) Nov 19, 2017
So now after showing your lie by claiming Peratt said something he did not, it is all an irrelevance. LOL!
Clearly this is not an auroral zone, nor is an auroral zone an extreme environment of the hypothetical neutron star. Alfvén must be a moron according to your statement, being he suggested diocotron instabilities in such a non-extreme environment.
You also must have missed the other statement made by Peratt, an actual plasma physicist, where he stated;
"Neglecting lightning, planetary atmospheres and hydrospheres are the only domains in the uniνerse where a non-hydromagnetic treatment of fluid dynamic problems is jυstifιed."
Ignorance is bliss, yes jonesdumb?
jonesdave
5 / 5 (4) Nov 19, 2017
As quoted by cantthink:
"...The instability leading to the filamentatiοn of the beam is known as the "slipping steam" or "diοcοtron" and occurs when charge neutrality is not locally maintained, for example, when electrons and ions separate.


And, pray tell, where in the data are you seeing that happen?
Hoist by your own petard, dear boy.
jonesdave
5 / 5 (4) Nov 19, 2017
And no, I didn't lie about Peratt. I quoted another plasma physicist, on ISF, explaining why the DI doesn't apply in a quasi-neutral plasma. Which is why you won't find anybody using it to model anything in a quasi-neutral plasma. As measured in-situ. Which part of that are you not understanding?
jonesdave
5 / 5 (4) Nov 19, 2017
It was at Cambridge in 1959 that Buneman discovered an instability that developed in two interpenetrating ***ion streams***; ..... While visiting Harvard......he was stimulated.....to work out a new instability in a ***collisional*** plasma involving a ***relative motion between electrons and ions driven by a quasi dc field*** in the direction transverse to the Earth's magnetic field.
While it was Buneman who first discovered the "slipping stream" or "diocotron" instability, Oscar credited..........The phenomenon is observed in cross-field microwave devices in which vortices develop throughout a ***charged-particle beam*** when a threshold determined by either the beam current or distance of propagation is surpassed. Alfven used the mechanism......to explain the folding of auroral curtains in the upper atmosphere.


A Tribute to Oscar Buneman - Pioneer of Plasma Simulation
http://plasmacosm...1994.pdf
Peratt is a co-author.

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