Researchers have evidence that might explain the unexpected presence of energetic electrons in Mercury's magnetic tail

April 17, 2018, American Institute of Physics
Credit: NASA

Theoretical physicists used simulations to explain the unusual readings collected in 2009 by the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) mission. The origin of energetic electrons detected in Mercury's magnetic tail has puzzled scientists. This new study, appearing in Physics of Plasmas, provides a possible solution to how these energetic electrons form.

Magnetic material's flow inside a planet creates a global magnetic field. In Mercury, and in Earth, liquid metal currents in the planetary cores induce the ' magnetic fields. These fields vary in shape, size, angle and strength from planet to planet, but are all important for protecting planets from solar particles.

Solar wind blasts planets with radiation and causes magnetic substorms, which we sometimes see on Earth as the northern lights. Magnetic tails or magnetotails form when intense radiation pressure from solar winds "pushes" on the planet's magnetic fields. These tails form on the nighttime side of the planet, facing away from the sun. On Mercury, in the tail are bigger and more rapid than those observed on Earth.

Mercury's magnetic field is 100 times weaker than Earth's, so it surprised physicists that MESSENGER detected signs of energetic electrons in the planet's magnetic tail—the Hermean magnetotail. "We wanted to find out why the satellite found ," said Xiaowei Zhou, an author of the study.

A likely candidate responsible for the presence of these energetic particles is . Magnetic reconnection occurs when the arrangement of lines change, releasing kinetic and thermal energy. However, in the turbulent astrophysical environment, magnetic reconnection is poorly understood. In this study, Chinese and German physicists investigated magnetic reconnection within the context of turbulence in the Hermean magnetotail.

Magnetohydrodynamic simulations and test particle calculations showed that plasmoids—distinct magnetic structures that encompass plasma—are generated during magnetic reconnection. These plasmoids accelerate . The simulation results are supported by MESSENGER measurements of plasmoid species and plasmoid reconnection in the Hermean magnetotail.

The researchers also used a mean-turbulence model to describe the turbulence of subgrid-scale physical processes. Acceleration processes were scaled to parameters that mimic characteristic conditions reported from the Hermean magnetotail. The simulations showed that in these conditions, turbulent plasmoid reconnection could be responsible for electron acceleration. "We also showed that turbulence enhances reconnection by increasing the reconnection rate," Zhou said.

The team's model predicts the upper limits for turbulent plasmoid and the corresponding electron acceleration. The Bepi-Colombo mission, due to launch October 2018, will test these predictions. The Bepi-Colombo satellites, built to withstand the harsh, hot environment near the sun, will be inserted into Mercury's orbit in 2025 for one Earth year to transmit observations from the planet.

"Previous satellites could not test the high energies from electrons and one aim of this mission is to measure the energetic particles from the Hermean magnetotail with new detector technology," Zhou said. With this new technology, the researchers hope to gain a more detailed subscale view of the effects of turbulence.

Explore further: MAVEN mission finds Mars has a twisted tail

More information: "Electron acceleration by turbulent plasmoid reconnection," Physics of Plasmas (2018). DOI: 10.1063/1.5011013

Related Stories

Studying magnetic space explosions with NASA missions

March 9, 2017

Every day, invisible magnetic explosions are happening around Earth, on the surface of the sun and across the universe. These explosions, known as magnetic reconnection, occur when magnetic field lines cross, releasing stored ...

Earth's magnetosphere

March 26, 2018

Enveloping our planet and protecting us from the fury of the Sun is a giant bubble of magnetism called the magnetosphere. It deflects most of the solar material sweeping towards us from our star at 1 million miles per hour ...

The solar wind breaks through the Earth's magnetic field

June 10, 2014

Space is not empty. A wind of charged particles blows outwards from the Sun, carrying a magnetic field with it. Sometimes this solar wind can break through the Earth's magnetic field. Researchers at the Swedish Institute ...

Recommended for you

Muons spin tales of undiscovered particles

April 20, 2018

Scientists at U.S. Department of Energy (DOE) national laboratories are collaborating to test a magnetic property of the muon. Their experiment could point to the existence of physics beyond our current understanding, including ...

Integrating optical components into existing chip designs

April 19, 2018

Two and a half years ago, a team of researchers led by groups at MIT, the University of California at Berkeley, and Boston University announced a milestone: the fabrication of a working microprocessor, built using only existing ...

16 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

RealityCheck
1.8 / 5 (5) Apr 17, 2018
@cantdrive85 and @jonesdave.

To try and forestall more of your mutual insults and feuding 'noise', I will just point out that newer crop of researchers are coming round to more correct description/labeling of what is happening. As I have long been pointing out, its the PLASMA FLOWS/CURRENTS/PLASMOID contents etc that "reconnect"; causing the magnetic fields to RE-arrange accordingly...as more researchers are increasingly acknowledging:
Chinese and German physicists investigated magnetic reconnection within the context of turbulence in the Hermean magnetotail.
Magnetohydrodynamic simulations and test particle calculations showed that plasmoids—distinct magnetic structures that encompass plasma—are generated during magnetic reconnection. These plasmoids accelerate energetic electrons. The simulation results are supported by MESSENGER measurements of plasmoid species and plasmoid reconnection in the Hermean magnetotail.
OK guys,take it from there. Play nice now, ok? :)
jonesdave
5 / 5 (5) 12 hours ago
OK guys,take it from there. Play nice now, ok? :)


What's to discuss? The article claims it is due to MRx. Cantthink claims that cannot happen. Their results are based on MHD sims, and cantthink claims MHD is invalid. So, it is fully in line with mainstream science, and completely at odds with the lightning bolt cultists.
cantdrive85
1 / 5 (3) 9 hours ago
The article claims it is due to MRx. Cantthink claims that cannot happen. Their results are based on MHD sims, and cantthink claims MHD is invalid.

The mainstream scientists were "surprised" by the "unexpected" energetic electrons. They were surprised because their models failed.
Then they invoke more pseudoscience such as "plasmoid reconnection" to find an ad hoc explanation. And jonesdumb thinks this is a success. LOL!
cantdrive85
1 / 5 (3) 8 hours ago
If they are invoking plasmoids, then there will be double layers. This is an undeniable fact, as such their MHD and MRx models are utterly useless. The double layers are part of a circuit and the entire system must be described as a circuit system.
BTW, "magnetic reconnection is pseudoscience" Hannes Alfven
jonesdave
5 / 5 (4) 8 hours ago
magnetic reconnection is pseudoscience" Hannes Alfven


"No, it isn't." Carl-Gunne Falthammar. And he would know a lot more about it than Alfven ever did.
jonesdave
5 / 5 (3) 7 hours ago
The mainstream scientists were "surprised" by the "unexpected" energetic electrons. They were surprised because their models failed.


So show me within the scientific literature (or elsewhere) where non-mainstream scientists predicted this. If you can't, then you are just blowing smoke out of your arse, as usual.

cantdrive85
1 / 5 (2) 7 hours ago
Energetic electrons are a side effect of double layers, and double layers in plasmas are ubiquitous. Any non plasma ignoramus would not be surprised by their mere presence.
jonesdave
5 / 5 (5) 7 hours ago
Energetic electrons are a side effect of double layers, and double layers in plasmas are ubiquitous. Any non plasma ignoramus would not be surprised by their mere presence.


Which double layers? I've read the paper, and they are nowhere to be seen. I also read some of the referenced material regarding the MESSENGER observations - again, no observation of double layers. Not seen in the simulations, not seen in-situ. Not required to explain anything. Ergo, the principle of parsimony says we can discount them.
Da Schneib
5 / 5 (4) 6 hours ago
Next up, @cantthink69 declares that @jones "denies the existence of plasma."

In 3,... 2,... 1,...
cantdrive85
1 / 5 (1) 6 hours ago
MESSENGER did not have the resolution to detect the double layers. Hell, it wasn't until MMS and Van Allen probes where multiple spacecraft were used was this phenomena definitively detected in near-Earth space. It takes a very specific resolution to be able to detect them.
However, anyone who has real laboratory experience with plasmoids will tell you that double layers absolutely are part and parcel to plasmoids. It is why the plasmoid has "structure", it is an undeniable fact.
And you are correct, their MHD models don't predict/resolve double layers, Alfvén said this long ago and is why MHD models are invalid.
"As neither double layer nor circuit can be derived from magnetofluid models of a plasma, such models are useless for treating energy transfer by menas of double layers."
Alfvén
"We may conclude that anyone who uses the merging concepts states bv implication that no double layers exist."
Also Alfvén
https://inis.iaea...18060222
jonesdave
5 / 5 (4) 6 hours ago
"We may conclude that anyone who uses the merging concepts states bv implication that no double layers exist."


So, that would be Falthammar and pretty much every plasma physicist alive, then. And yet I know a PP who is perfectly fine with reconnection, yet did his PhD on DLs at Alfven's lab in Sweden. Have a look at the Wikipedia entry on DLs - I think he wrote a fair chunk of it.
The problem with EU is that they have no plasma physicists amongst them, and therefore continually have to call on misinterpretations of stuff Alfven said decades ago. They don't have anyone capable of understanding the subject themselves, and the subject has moved on in the 25 years plus since Alfven had anything to do with it.
cantdrive85
1 / 5 (2) 5 hours ago
So, that would be Falthammar and pretty much every plasma physicist alive, then.

Yep, and why the plasma ignoramuses are always surprised, shocked, perplexed, and continuously find that which is unexpected, like the story above points out.
Have a look at the Wikipedia entry on DLs - I think he wrote a fair chunk of it.

I can tell it was written by a plasma ignoramus, he keeps referring to laboratory power supplies yet seems to fail to comprehend the power supply in natural plasmas. Typical of a plasma ignoramus unable to grasp there is electric energy in plasmas.
Da Schneib
5 / 5 (2) 5 hours ago
Plus plasma physics is now all full of scary integrals and PDEs. And stuff.

For every phenomenon there is a hypothesis that is simple, easy, obvious, and completely, idiotically wrong.
jonesdave
5 / 5 (2) 4 hours ago
Yep, and why the plasma ignoramuses are always surprised, shocked, perplexed, and continuously find that which is unexpected, like the story above points out.


Nope. They get far more right than wrong. And, let's be honest, you lot never get anything right, as you don't have anyone that can even do plasma physics. You never produce anything, other than whining on places like this. You are incapable of doing the science, but see fit to criticise it. Rank hypocrisy, I call that. Now, what is a collisionless plasma again? Pot and kettle, eh?
jonesdave
5 / 5 (2) 4 hours ago
Typical of a plasma ignoramus unable to grasp there is electric energy in plasmas.


Why don't you tell him woo boy? Just sign up at ISF or Cosmoquest, and away you go. However, we all know you have neither the cojones nor the knowledge to be able to debate an actual plasma physicist. You just want to do your Dunning-Kruger, Walter Mitty stuff on here, for whatever weird psychological reasons.
cantdrive85
not rated yet 48 minutes ago
Just sign up at ISF or Cosmoquest, and away you go

He is welcome here too. You're such good friends you should invite him on over.

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.