Large scale electric fields in coronal flare circuits

[michaelmozina]

Two new papers were published on Arxiv last week that both discuss solar flares from the perspective of the electric field rather than the magnetic field. They both seem to compliment each other quite nicely.

http://arxiv.org/abs/0908.0813

In summary, in the solar atmosphere electric circuits can be driven by an electric power supply induced by the photospheric motion in a bipolar active region. If these electric circuits are closed via the corona, and electric field is established along the coronal loop. Electrons can be accelerated along these large scale DC electric fields.

http://arxiv.org/abs/0908.0384

The ropes originated inside a funnel-like magnetic domain whose base was bounded by an EUV ring structure, and the top was associated with a coronal null point. The ropes appear to be the major drivers for the events, but their rise was not triggered by reconnection in the coronal null point. We propose a scenario and a three-dimensional scheme for these events in which the filament eruptions and flares were caused by interaction of the ropes.

The second paper talks about flares being caused by interacting "magnetic ropes" which Alfven described in the following way:

"However, in cosmic plasmas the perhaps most important constriction mechanism is the electromagnetic attraction between parallel currents . A manifestation of this mechanism is the pinch effect, which was studied by Bennett long ago (1934), and has received much attention in connection with thermonuclear research . As we shall see, phenomena of this general type also exist on a cosmic scale, and lead to a bunching of currents and magnetic fields to filaments or `magnetic ropes' . This bunching is usually accompanied by an accumulation of matter, and it may explain the observational fact that cosmic matter exhibits an abundance of filamentary structures (II .4 .1) . This same mechanism may also evacuate the regions near the rope and produce regions of exceptionally low densities."

 

[harrycostas]

G'day Michael

The process is probably one of the most important processes in explaining many formations from supernova to galaxy evolutiion.

 

[UFmbutler]

The second paper would have been nice to have back when I had the energy to discuss this actively a couple years ago

I'm not sure what to make of it. It states that an electrical field of some given strength in the solar atmosphere can accelerate electrons to the energies we see in the solar wind(~200 keV). Do we know where the electrons are actually accelerated though, and how do we know the electric field is the only thing that accelerates them, or if it even plays a major role? I think the paper does present an alternative that may or may not be true, but what I don't like about it is that it doesn't address the alternative(i.e., the mainstream theory of magnetic reconnection, which also has equally or greater detailed papers to explain how the acceleration occurs). I think that in order for a new theory to become accepted it must prove itself to be correct, but also show that the mainstream theory is wrong, or at least that the new one can explain things better. If no real errors can be found in either, then perhaps it is a little of both. This theory coudl very well be true, but it makes me cautious when they don't address the question everyone from the mainstream who reads it will be asking: "what about reconnection?".

I don't want to get into another discussion of whether magnetic reconnection as it is understood today (i.e. not the literal reconnecting of magnetic field lines but rather a change in field topology) can accelerate electrons or not, but that is the current mainstream belief. I think, if all the assertions are valid, which to be honest I don't know because I know little to nothing about circuit theory, then it is worth consideration. I know the mainstream papers don't discuss circuits, but as far as I know this is the first modern paper I've seen that says "the solar atmosphere can be modeled as a circuit and here's why" clearly, so maybe it will get attention, maybe not. I'm not familiar with the journal it was published in so we'll see.

 

[michaelmozina]

The second paper would have been nice to have back when I had the energy to discuss this actively a couple years ago

I agree, it would have been very nice.....

I'm not sure what to make of it. It states that an electrical field of some given strength in the solar atmosphere can accelerate electrons to the energies we see in the solar wind(~200 keV). Do we know where the electrons are actually accelerated though, and how do we know the electric field is the only thing that accelerates them, or if it even plays a major role?

Well, I would think that same question would apply to every theory we might come up with, but in this case there are actually empirical experiments by Birkeland to back up the electrical field idea, not to mention the other paper.

I think the paper does present an alternative that may or may not be true, but what I don't like about it is that it doesn't address the alternative(i.e., the mainstream theory of magnetic reconnection, which also has equally or greater detailed papers to explain how the acceleration occurs).

Actually the second paper seems to address the "magnetic reconnection" argument. From the abstract:

We have revealed that these apparent ``cusps'' were most likely mimicked by twisted magnetic flux ropes, but unlikely to be related to the inverted Y-like magnetic configuration in the standard flare model. The ropes originated inside a funnel-like magnetic domain whose base was bounded by an EUV ring structure, and the top was associated with a coronal null point. The ropes appear to be the major drivers for the events, but their rise was not triggered by reconnection in the coronal null point. We propose a scenario and a three-dimensional scheme for these events in which the filament eruptions and flares were caused by interaction of the ropes.

The advantage of looking at these ropes as "circuits" is that circuits can intersect at any location, not simply at a 'magnetic null point' and the total circuit energy of both intersecting circuits determines the outcome at the physical point of reconnection.

I think that in order for a new theory to become accepted it must prove itself to be correct, but also show that the mainstream theory is wrong, or at least that the new one can explain things better.

That "seems" to be the intent of the second paper on magnetic ropes, whereas the other paper does not seem to be attempting to eliminate any other possible explanations.

If no real errors can be found in either, then perhaps it is a little of both. This theory coudl very well be true, but it makes me cautious when they don't address the question everyone from the mainstream who reads it will be asking: "what about reconnection?".

Well, here's what the second paper states in the conclusion:

4. Conclusion
The combined multi-spectral analysis of two homologous eruptive events of 2002 June 1
and 2 allowed us to outline their common picture. Similarity of the photospheric conditions and
persistent photospheric flows determined the resemblance between the events. The boundary
of the sites where the events occurred was a time-evolving structure visible in EUV as a ring.
The observations left the impression that it was not possible to perceive the scenarios
of the events by considering each of them separately. We have combined all the observed facts
from both these events, as if they were a single event, and proposed their common scenario.
We have concluded that their major drivers were eruptions of magnetic flux ropes. Neither the
triggering of the events nor their evolution appear to be controlled by processes at the coronal
null point. Such processes were probably present, but they did not determine the initiation
of the events. The standard model, the breakout model, as well as other models employing
magnetic reconnection high in the corona do not help to understand these impulsive events.

You'd have to read the whole paper to understand their logic, but they do attempt to 'explain' these events with standard "magnetic reconnection" theory and don't seem to find it to be a viable candidate. They tend to use the term "reconnection" the way *I* might use that term by the way, to denote the physical point of loop reconnection. They tend to use the term 'magnetic reconnection' (both words) when referring to standard "magnetic" reconnection theories.

I don't want to get into another discussion of whether magnetic reconnection as it is understood today (i.e. not the literal reconnecting of magnetic field lines but rather a change in field topology) can accelerate electrons or not, but that is the current mainstream belief. I think, if all the assertions are valid, which to be honest I don't know because I know little to nothing about circuit theory, then it is worth consideration. I know the mainstream papers don't discuss circuits, but as far as I know this is the first modern paper I've seen that says "the solar atmosphere can be modeled as a circuit and here's why" clearly, so maybe it will get attention, maybe not. I'm not familiar with the journal it was published in so we'll see.

My point in posting it here was in the hope that it might 'get some attention'. We'll have to wait and see.

 

[UFmbutler]

Sorry, by second paper I meant the first. I didn't get a chance to look at the second one beyond the abstract, but it does indeed address reconnection.

 

[michaelmozina]

Sorry, by second paper I meant the first. I didn't get a chance to look at the second one beyond the abstract, but it does indeed address reconnection.

FYI, checkout the CME/sunspot thread. There's something happening today that you might be interested in.

 

[michaelmozina]

UFMButler:

Instead of hijacking the stellar core thread, and rather than get into the whole topic of EU theory, how about we focus on the two papers I posted earlier and this paper that also describes the return currents in the solar atmosphere?

http://arxiv.org/abs/0806.1701

 

[harrycostas]

G'day Michael

I came across this paper while reading papers on the Sun's Dynamo and the cyclic events relating to sun spots.

I think this paper is in line with your discussion.

http://arxiv.org/abs/0908.1137
Coronal Implosion and Particle Acceleration in the Wake of a Filament Eruption

Authors: Rui Liu, Haimin Wang
(Submitted on 8 Aug 2009)

Abstract: We study the evolution of a group of TRACE 195 A coronal loops overlying a reverse S-shaped filament on 2001 June 15. These loops were initially pushed upward with the filament ascending and kinking slowly, but as soon as the filament rose explosively, they began to contract at a speed of ~100 km/s, and sustained for at least 12 min, presumably due to the reduced magnetic pressure underneath with the filament escaping. Despite the contraction following the expansion, the loops of interest remained largely intact during the filament eruption, rather than formed via reconnection. These contracting loops naturally formed a shrinking trap, in which hot electrons of several keV, in an order of magnitude estimation, can be accelerated to nonthermal energies. A single hard X-ray burst, with no corresponding rise in GOES soft X-ray flux, was recorded by the Hard X-ray Telescope (HXT) on board Yohkoh, when the contracting loops expectedly approached the post-flare arcade originating from the filament eruption. HXT images reveal a coronal source distinctly above the top of the soft X-ray arcade by ~15". The injecting electron population for the coronal source (thin target) is hardening by ~1.5 powers relative to the footpoint emission (thick target), which is consistent with electron trapping in the weak diffusion limit. Although we can not rule out additional reconnection, observational evidences suggest that the shrinking coronal trap may play a significant role in the observed nonthermal hard X-ray emission during the flare decay phase.

 

[michaelmozina]

G'day Michael

I came across this paper while reading papers on the Sun's Dynamo and the cyclic events relating to sun spots.

I think this paper is in line with your discussion.

http://arxiv.org/abs/0908.1137
Coronal Implosion and Particle Acceleration in the Wake of a Filament Eruption

Authors: Rui Liu, Haimin Wang
(Submitted on 8 Aug 2009)

Abstract: We study the evolution of a group of TRACE 195 A coronal loops overlying a reverse S-shaped filament on 2001 June 15. These loops were initially pushed upward with the filament ascending and kinking slowly, but as soon as the filament rose explosively, they began to contract at a speed of ~100 km/s, and sustained for at least 12 min, presumably due to the reduced magnetic pressure underneath with the filament escaping. Despite the contraction following the expansion, the loops of interest remained largely intact during the filament eruption, rather than formed via reconnection. These contracting loops naturally formed a shrinking trap, in which hot electrons of several keV, in an order of magnitude estimation, can be accelerated to nonthermal energies. A single hard X-ray burst, with no corresponding rise in GOES soft X-ray flux, was recorded by the Hard X-ray Telescope (HXT) on board Yohkoh, when the contracting loops expectedly approached the post-flare arcade originating from the filament eruption. HXT images reveal a coronal source distinctly above the top of the soft X-ray arcade by ~15". The injecting electron population for the coronal source (thin target) is hardening by ~1.5 powers relative to the footpoint emission (thick target), which is consistent with electron trapping in the weak diffusion limit. Although we can not rule out additional reconnection, observational evidences suggest that the shrinking coronal trap may play a significant role in the observed nonthermal hard X-ray emission during the flare decay phase.

Thank you for the link. I'll probably have some time this weekend to read it, but already I can see that this is a related paper to be sure. The interesting thing in the abstract is that they talk about the movement of plasma and the acceleration of electrons and they also seem to eliminate "magnetic reconnection" as a "cause". Such events are consistent with atmospheric discharge processes that are known to emit x-rays on virtually every planet in the solar system with an atmosphere. It is only logical that this process would also occur inside the atmosphere of the largest body in the solar system.

 

[harrycostas]

G'day Michael


I wish I had your poetic words, being dislexic puts my words upside down and inside out. Maybe that's why I come from the land down under.

This link is quite informative
http://www.electric-cosmos.org/sun.htm
Hannes Alfven's Solar Prominence Circuit
and
Primary and secondary electric currents in the Sun.
http://lh6.ggpht.com/mgmirkin/R4C-iYbAt ... ircuit.jpg

We are still many years away from understanding the workings of the Sun. The trap that some fall in is "KNOWING"

 

[MeteorWayne]

michael, if you allow this to become an EU discussion, you know where it will wind up....

 

[michaelmozina]

michael, if you allow this to become an EU discussion, you know where it will wind up....

It is my hope that we can keep this thread focused on a "coronal loop" discussion. What are they made of? What causes them to reach millions of degrees? The three recent papers I have cited are fairly "new" evidence in terms of the mathematical support for the idea of return currents, and electrical processes in coronal loop formation. The last paper that Harry cited is also a paper about coronal loops, albeit one skewed toward an explanation based upon "magnetic funnels". Each of these papers are directly related to the makeup and composition of coronal loops. It should be an interesting discussion, but nobody can accuse the authors of any of these papers for not mathematically supporting their case. Their explanations are not 'unexplained' in any way.

Such papers do of course directly suggest that coronal loops might be related to discharge processes in plasma, and in that sense, it will tend to suggest something that I happen to agree with. How do we keep this fair in light of these new mathematical analysis provided by these various authors over the past year?

FYI, Harry's paper might be the one you should start with and then the Russian one. Between the two of these papers, you get both a mainstream and current flow oriented explanation of these processes, and both papers seem to have a common denominator, the all describe a "magnetic rope" in plasma from both the E field and B field perspective. It's really interesting stuff IMO, but certainly not "unexplained" in either orientation.

All these papers do have implications in terms of "flares" and how they manifest themselves in a light plasma atmosphere. It does have "EU" applications, but the seems to be easily resolved by not discussing anything other than solar atmospheric activity, and leaving everything else that is irrelevant out of the discussion.