Flux Ropes in the Solar Wind

[celeste]

When charged particles are moving along the lines of an external magnetic field, they spin around the lines of force, due to the Lorentz force, forming a true Birkeland current. For there not to be a spin, there has to not be an external magnetic field, in which case it isn't a Birkeland current.

You are making the same fundamental assumption that we all made before Dr. Scott came along. You are right, that if a single charged particle travels in an external field, it can only travel along the field lines, or spiral around it, due to the Lorentz force. But as the current density increases, the spiraling charged particles themselves become the basis of magnetic fields, which then affect the other particles. This is what Donald Scott is modeling. It's only if we keep the plasma density very low, and the background magnetic field very high, that we can use that fundamental assumption of charged particles spiraling in the background magnetic field.
With his idea comes another. If the magnetic lines spiral around the filament, we can have charged particles spiraling around the filament (bound by electrostatic forces), yet traveling along the magnetic lines of the filament. It appears that the particles are spiraling around due to the background magnetic field (they still spiral along the same axis). That is probably why no one figured out what was going on this whole time.

[celeste]

This article http://atp.uclan.ac.uk/buddypress/diffusion/?p=1532 will show that flux tubes are exactly the same as the Birkeland currents that Donald Scott models.
The mainstream calls them "twisted flux tubes", but they are just Scott's filaments, with an outer radius where the field is NOT axial. Remember, "normal" flux ropes have an axial field at there surface.

Interesting how the mainstream is getting to the same model as Scott did, by approaching the problem from the opposite end:
Donald Scott started with Birkeland currents, and derived mathematically that they should have helical magnetic fields. The mainstream observes "flux tubes" that have helical fields, and calls them "twisted flux tubes", without realizing that they are just Birkeland currents. Notice they apply the boundary conditions "intrinsically, there is no radial component of the magnetic field of a flux tube", "however, the twist must still be outlined for all boundary conditions".

This is almost comical. Donald Scott comes up with a model of Birkeland currents where magnetic fields have variable helicity, and we debate whether or not that model works in the real world. In the mean time, the mainstream sees these "tubelike" structures that do vary in magnetic helicity at there surface, calls them "flux tubes", and tries to understand mathematically how/why they work. All this, because none of us (EU or mainstream), had a correct model of Birkeland currents before Dr. Scott.

[CharlesChandler]

This article http://atp.uclan.ac.uk/buddypress/diffusion/?p=1532 will show that flux tubes are exactly the same as the Birkeland currents that Donald Scott models.

These are not at all the same type of currents. The paper that you referenced was just a modeling exercise. The only source data mentioned that was relevant to the study of flux ropes in the solar wind was this (with my bolding):

Régnier, S, Amari, T. (2004) 3D magnetic configuration of the Hα filament and X-ray sigmoid in NOAA AR 8151. Astronomy and Astrophysics 425, 345-352

We investigate the structure and relationship of an Hα filament and an X-ray sigmoid observed in active region NOAA 8151. We first examine the presence of such structures in the reconstructed 3D coronal magnetic field obtained from the non-constant-α force-free field hypothesis using a photospheric vector magnetogram (IVM, Mees Solar Observatory). This method allows us to obtain several flux systems (filament, coronal loops or sigmoid) with different physical properties (strength and sign of the electric current density, shear or twist). By searching for magnetic dips in the configuration, we clearly identify the filament structure which is in a good agreement with Hα observations. We find that both filament and sigmoidal structures can be described by a long twisted flux tube with a number of turn less than 1 (∼0.5-0.6 turn) which means that these structures can be considered as stable. We also compare the geometrical parameters of the filament, the sigmoid, a quasi-potential flux tube and the highly twisted flux tube. The filament is lower (∼ 30 Mm) in the corona than the other flux systems (40-60 Mm). The filament and the sigmoid have similar absolute values of α and Jz on the photosphere, however the electric current density is positive in the filament and negative in the sigmoid: the filament is right-handed whereas the sigmoid is left-handed. This fact can explain handedness differences between magnetic clouds and their solar progenitors (twisted flux bundles in the low corona). The mechanism of eruption in AR 8151 is more likely not related to the development of instability in the filament and/or the sigmoid but is associated with the existence of a highly twisted flux tube (∼ 1.1-1.2 turns).

This is a "twisted pair" of Birkeland currents of opposite charges, each with an undifferentiated core, and bound together by the electric force, while kept separate by the magnetic force.

http://qdl.scs-inc.us/2ndParty/Images/C ... el_wbg.png

The reason for the twist is that +ions are heavier than electrons, so the opposing magnetic fields that keep the two charge streams separate also impart a rotary motion on the lighter of the two streams. Thus the negative sigmoid spirals around the positive filament.

This is very different from Scott's model, in which there is only one sign of charge, in a layered configuration.

[celeste]

however the electric current density is positive in the filament and negative in the sigmoid: the filament is right-handed whereas the sigmoid is left-handed. This fact can explain handedness differences between magnetic clouds and their solar progenitors (twisted flux bundles in the low corona).

Charles,
Tell me how they know the current density is positive in the filament, and negative in the sigmoid? Don't say it is because the filament is right-handed whereas the sigmoid is left-handed. This is the very argument that Scott's model is countering. We know the direction a single charged particle should spiral, once we know the background magnetic field direction. If Scott's model is right, we can not tell sign of charge by handedness of spiraling in a B.C.
So again, what are the measurements (presumably particle velocities?) that tell us the current density is positive in the filament, and negative in the sigmoid?

Charles, I may sound confrontational, but I'm really just trying to learn here. As you suggested elsewhere, it is better just to state a theory as fact, and let others rip it apart if it is wrong, before we get to attached to it ourselves. This is the spirit I'm intending.

[ZenMonkeyNZ]

Keep up the discussion, guys! Great material and plenty of references to explore.

[Solar]

IMO, what he's showing can only be created by a contrived apparatus, in which case it doesn't speak to in situ astrophysical conditions.

This idea is quite dismissive and counterproductive. I guess I’m not understanding how it is that you’re not understanding that Dr. Scott’s paper ‘unwinds’ the sigmoid producing filament and looks at it from a ‘minimum energy configuration” wherein cylindrical coordinates are used, and yes; noting that “these magnetic components reverse directions”. This is explained at the onset. Also stating on pg 2 that this minimal energy configuration indicates that:

… the magnetic field and the current that causes it will not push or pull on each other when they are exactly aligned. Such an arrangement is termed a field-aligned current.

That means no sigmoid producing filamentary twist; just cylindrical concentric ‘sheaths’ instead.

One is basically looking at “radial distance, r, measured outward from the central z-axis of the Birkeland current stream.” - being portrayed. Therefore no twist but instead “field aligned” layered sheaths extending outward (or inward depending on one’s POV) from the axis as stated. To compare the observed in situ situation (with the presence of sigmoids) wherein energy configuration is MUCH greater than a minimum with the presence of time varying electric and magnetic fields ‘pushing and pulling’ on one another to induced a twist in conjunction with Dr. Scott’s paper wherein the serpentine quality (excluding the potential expressed via the Bessel relation) is not presented and fail to recognize and correlate the difference is no reason to dismiss. Therefore on page 11:

… concentric cylinders of concentrated matter that surround the axis of the current. These layers are separated by regions from which matter is swept away (both upward and downward) toward the neighboring regions of high matter concentration. This ionized matter constitutes a set of concentric, hollow, cylindrical, conducting paths.

This is why one has the photographs of concentric configurations from pages 8-11. They appear to exemplify that “minimum energy configuration” (“dampened” or “screened” electric field) and therefore not a twisting sigmoid signature but a ‘disk’ of concentric rings as the cylindrical aspects pointed out with the image of the bipolar nebula. Its not a “contrived apparatus” as you’ve characterized it but a failure to correlate different evolutionary aspects of the filaments that may evolve under the influence of time varying fields.

[CharlesChandler]

Tell me how they know the current density is positive in the filament, and negative in the sigmoid? Don't say it is because the filament is right-handed whereas the sigmoid is left-handed. This is the very argument that Scott's model is countering. We know the direction a single charged particle should spiral, once we know the background magnetic field direction. If Scott's model is right, we can not tell sign of charge by handedness of spiraling in a B.C. So again, what are the measurements (presumably particle velocities?) that tell us the current density is positive in the filament, and negative in the sigmoid?

It isn't the particle velocity that is evidence of the handedness -- it's the polarity of the magnetic field, per Ampere's law. I don't have access to the whole article, so I put it on my library list, and I'll let you know if the full article says anything different.

Charles, I may sound confrontational, but I'm really just trying to learn here. As you suggested elsewhere, it is better just to state a theory as fact, and let others rip it apart if it is wrong, before we get to attached to it ourselves. This is the spirit I'm intending.

Absolutely! I'm not always right, but the nice thing about making explicit statements is that you find out really fast when you're wrong. So let's hear them!

… the magnetic field and the current that causes it will not push or pull on each other when they are exactly aligned. Such an arrangement is termed a field-aligned current.

That means no sigmoid producing filamentary twist; just cylindrical concentric ‘sheaths’ instead.

I don't know what kind of field the current would be aligned to, if the particles are actually paralleling the field (instead of spiraling around it) without there being a Lorentz force. In Scott's "concentric shell" model, the local B-fields might overpower the external field, leaving nothing to generate a Lorentz force. But then I don't understand why it would still be worth calling it a "field-aligned current", if the external field was that weak. Also, I don't understand how the current could ramp up in an external field, until it got to the current density capable of overpowering the external field, without initially spiraling. And once the spiraling starts, it is a much more complex environment, that isn't going to just unravel itself into a straight-line current. (The tortuous paths of electrons in lightning is a good example of how a current that ramps up quickly is still heavily influenced by a weak external magnetic field.) So I'm thinking that the "concentric shell" current can only be created by an instantaneous impulse, as in focus fusion, hence the charge of contrivance. Furthermore, this isn't the way Birkeland described auroral currents, nor have I seen this configuration described anywhere else except in the focus fusion literature, so I don't see how Scott is justified in saying that the concentric shell configuration is typical of Birkeland currents.

To compare the observed in situ situation (with the presence of sigmoids) wherein energy configuration is MUCH greater than a minimum with the presence of time varying electric and magnetic fields ‘pushing and pulling’ on one another to induced a twist in conjunction with Dr. Scott’s paper wherein the serpentine quality (excluding the potential expressed via the Bessel relation) is not presented and fail to recognize and correlate the difference is no reason to dismiss.

I'll give you $10 if you can diagram that sentence. Anyway...

The concentric shells in the plasma focus that is pictured on page 9 were caused by an instantaneous discharge of 174,000 amps within a specially designed apparatus, and yes, I'm questioning the applicability.

This is why one has the photographs of concentric configurations from pages 8-11. They appear to exemplify that “minimum energy configuration” (“dampened” or “screened” electric field) and therefore not a twisting sigmoid signature but a ‘disk’ of concentric rings as the cylindrical aspects pointed out with the image of the bipolar nebula. Its not a “contrived apparatus” as you’ve characterized it but a failure to correlate different evolutionary aspects of the filaments that may evolve under the influence of time varying fields.

You're assuming the conclusion. IF Birkeland currents actually had concentric shells, and IF there was a current passing through the nebula and the planet pictured, the model would explain the observations. But when the only laboratory evidence of concentric shell currents is from experimentation on rare and highly unstable configurations, and where the in situ electromotive force hasn't been identified, and is arguably not possible as asserted, it isn't exactly a complete explanation.

[celeste]

Solar and Charles,
Here https://www.youtube.com/watch?v=8LA-Tg29050 (Butterfly Nebula animation)
we have what looks like a single filament with concentric shells, yet if you watch the last 15 seconds of the video, it seems that what could appear as a sigmoid, is the green region of that filament. Depending on our imaging (which may be dependent on the scale of the filament), we may only perceive this object as a sigmoid (green area in the video), spiraling around a more massive filament (the red area, or even one shell of the red area). Can we say for certain, that the flux tube behavior is NOT this?

[CharlesChandler]

Can we say for certain, that the flux tube behavior is NOT this?

You're assuming that it's a flux tube, and that plasma focus behaviors are relevant. I'm questioning both of those assumptions.

[CharlesChandler]

The bottom line here is that flux tubes in the solar wind are well described as simple Birkeland currents, which are just electric charges moving in the presence of an external magnetic field, where the Lorentz force causes the charged particles to spiral around the magnetic lines of force.

The tubes match up 1:1 with granules on the solar surface, which makes sense if the current exiting the Sun has a higher velocity coming up through the updrafts in the center of the granules, as opposed to fighting against the downdrafts around the outsides. The faster currents in the centers then develop discrete magnetic pinches, which organize them into individual "flux tubes" emanating from the surface of the Sun.

It also makes sense that the "fast wind" emanates from regions where the lines of force of the Sun's magnetic field are perpendicular to the surface (i.e, at the poles during the quiescent phase). This way, the currents stream straight away from the Sun, following those lines of force. Where the Sun's field is perpendicular to the surface, the charged particles are deflected into movement that is also perpendicular to the surface, braking their outward flow.

This deflection of Birkeland currents in an external field accounts for the helmet streamers, which begin with broad bases on the surface of the Sun, and pinch down to narrow filaments at the outer extents of the corona. The magnetic field lines correspond precisely to the shape of the helmet streamers, where the base reveals the general toroidal form of the Sun's field. But the tips of the streamers, and their "open field lines", require just a tad more thought. While the currents are deflected in the direction of the B-field, which funnels polar currents toward a point of convergence nearer the equatorial plane, in the end, the currents are ultimately headed out into the heliosphere. When they break out of the Sun's toroidal field, they drag the Sun's lines of force with them, which have become the axial fields in Birkeland currents.

As the Sun rotates, and with a helmet streamer constantly emitting charged particles in Birkeland currents, it produces a water-sprinkler effect, with a sheet-like spray. This is known as the heliospheric current sheet, which is made up of individual Birkeland currents known as flux tubes.

When these Birkeland currents enter the influence of the Earth's magnetic field, they once again align themselves to the external field, so they now assume the toroidal form of the Earth's field, just like they were first organized into the toroidal form of the Sun's field inside the helmet streamers. Because both polarities of magnetic fields are present in the heliospheric current sheet (since both polarities were present at the surface of the Sun), the Birkeland currents get sorted according to polarity. Currents that originated within a south magnetic pole on the surface of the Sun get directed toward the North Pole of the Earth. This might require that the Birkeland currents weave their way past each other during the sorting process. Such weaving has been observed, and always corresponds with the magnetic polarity of the Birkeland currents, so there's no doubt that geomagnetic sorting is the driving force.

Once the Birkeland currents get to where the Earth's lines of force are converging toward the poles, the particles are accelerated by the magnetic force (since the Birkeland currents are acting as electromagnets that can be accelerated just like bar magnets), from < 700 km/s, up to 60,000 km/s, or 1/5 the speed of light. At such extreme velocities, particle collisions generate the luminosity known as the aurora. The negatively charged particles are also attracted to the positively charged ionosphere.

Nearing the surface, the lines of magnetic force are no longer converging, and thus the primary accelerating force goes away. Also, once the electrons get to the bottom of the ionosphere at 85 km above the surface, the electrostatic attraction is no longer downward, but rather upward, and thus the accelerating force turns into a decelerating force. So the electrons slow down, and the +ions catch up. Once the electrons and +ions are traveling the same speed, they become candidates for recombination, releasing photons in the process. This often produces a distinct brightening of the aurora at its base. Then the aurora stops abruptly at roughly 80 km above the surface, because all of the opposite charges have recombined. The neutral atoms and molecules are then invisibly dispersed.

Still, the surface of the Earth is negatively charged, which attracts +ions and repels free electrons. So any time a molecule gets photo-ionized, the +ion will drift toward the Earth, and the free electron will drift away. This produces a net flow of electrons away from the Earth, which accumulate in the Van Allen belts. From there, the electrons drift back into the solar wind in the magnetotail, where once again Birkeland currents with axial magnetic fields split a toroidal magnetic field into "open field lines", just like they did in the helmet streamers.

Did I leave anything out?

[CharlesChandler]

Where the Sun's field is perpendicular to the surface, the charged particles are deflected into movement that is also perpendicular to the surface, braking their outward flow.

This should have said:

Where the Sun's field is parallel to the surface, the charged particles are deflected into movement that is also parallel to the surface, braking their outward flow.

Sorry for the confusion.

[upriver]

Still, the surface of the Earth is negatively charged, which attracts +ions and repels free electrons. So any time a molecule gets photo-ionized, the +ion will drift toward the Earth, and the free electron will drift away. This produces a net flow of electrons away from the Earth, which accumulate in the Van Allen belts. From there, the electrons drift back into the solar wind in the magnetotail, where once again Birkeland currents with axial magnetic fields split a toroidal magnetic field into "open field lines", just like they did in the helmet streamers.

Did I leave anything out?

Really nice!

To extend your essay, I would add the dynamic aspects of the flux tube.
When the tube is initially formed the current is driven through it like a standard wire following the right hand rule. As the current increases it pinches(reconnects) causes a change in configuration of the flux tube to a field aligned current possibly because the Curl field constricts causing a very small gyroradius in the centers of the tube, which then collapses and reforms with a standard RH rule current. The field aligned current is really where the core plasma is on such a tight gyro radius the it looks to be strictly field aligned. The dynamic behaviour alternates between these 2 modes. These are the conclusions that I came to from reading CLUSTER, THEMIS and other sat papers about FTEs. It may that most flux tubes(from the photosphere granules to the heliosphere) are constant and its only the one that enters the magnetosphere(double layers?) is subject to such dynamic activity.

Brant

[celeste]

The bottom line here is that flux tubes in the solar wind are well described as simple Birkeland currents, which are just electric charges moving in the presence of an external magnetic field, where the Lorentz force causes the charged particles to spiral around the magnetic lines of force.

I agree that flux tubes are Birkeland currents, but I don't think it's the external magnetic field that dominates how charges move in the filament.

Let's look at how a coronal loop erupts into a CME outburst, from two different approaches:
1. We can take the approach that our coronal loop follows the background magnetic field lines exactly. Here then, as you suggest, it is the Lorentz force that causes the particles to spiral around the filament axis. If the filament erupts, and sends particles streaming outwards from the sun, it is because the background magnetic field lines have "snapped" and reconnected into a field that carries the particles away from the sun. This idea of reconnection of the background field, is the mainstream approach.
2. We can take the approach that the magnetic field of the particles in the loop are what keep the loop together. In this case, the loop need not be following the background magnetic field at all. When the loop erupts, particles then get dumped into the background magnetic field, and follow the magnetic field that was ALREADY THERE.

The choices are that either the particles always follow the background (larger scale)magnetic field, where the field itself changes from a loop to lines streaming from the sun, or the particles flow in a small scale scale filament, which erupts and leaves our particles only then being dominated by the background magnetic field. I'm arguing the latter case.

Now, I would like to point out why we may have misinterpreted what is happening:
when we measure magnetic field strength by Faraday rotation, we are actually measuring the magnetic field strength,combined with how many free electrons are in that magnetic field. So if a small scale filament erupts into the background magnetic field, it may look like the background magnetic field is increasing in strength,as the filament's field appears to decrease. It may look like our looped shaped magnetic field has "reconnected" into the background magnetic field. In actuality, when a filament "explodes" ,its magnetic field vanishes. We just make the background magnetic field appear stronger, by dumping all those charged particles into that field.

[CharlesChandler]

Really nice! [...] As the current increases it pinches (reconnects) causes a change in configuration of the flux tube to a field aligned current possibly because the Curl field constricts causing a very small gyroradius in the centers of the tube, which then collapses and reforms with a standard RH rule current.

Thanks! I agree that there is a configuration change, while I guess I would phrase it differently -- I'd say that the flux tube kinda-sorta didn't exist, until the current increased to the point that it started generating its own magnetic field. Then the magnetic pressure between that and the external field forced the configuration change. So I think that there is a very slow, radial, outward drift of electrons that are equally distributed by electrostatic repulsion across the entire surface of the Sun. Only once they get past the resistance in the photosphere do they get accelerated to velocities capable of electrodynamics. So the photosphere~chromosphere boundary is where the flux tubes are born. Only in sunspots do the currents inside the photosphere get strong enough for electrodynamic behaviors. This is an important point, since the biggest problem with any electric Sun theory is explaining the current regulator. Those flux tubes should get pinched into a very small number of very powerful currents (like in a plasma lamp), so why don't they? If the electrons are sitting on a current divider, attracted to a positive charge deeper inside the Sun, and also to a positive charge in the heliosphere, the electrons will drift slowly at first, but will pick up speed as they move away from the Sun, especially when they get past the resistance in the photosphere and into the near-vacuum of the chromosphere. So that's when they become Birkeland currents.

BTW, are you going to issue predictions of flare-ups of C/2013 A1 in mid-October? Postdiction of past cometary flare-ups, compared to solar wind parameters, is legitimate work, but you shouldn't miss the chance to be the first to predict such things.

I agree that flux tubes are Birkeland currents, but I don't think it's the external magnetic field that dominates how charges move in the filament.

Hang on a second. If the external magnetic field isn't dictating helical particle motion, it isn't a Birkeland current! There are tight and loose usages of the term, but if we're talking specifics, we need to agree on the definitions, and I'm talking about Birkeland currents in the original sense. Any other configuration should be clearly identified, such as a "Scott current" or a "focus fusion current", just so we can keep it all straight.

Let's look at how a coronal loop erupts into a CME outburst...

Much of the literature on this topic confuses the issue, but coronal loops do not actually erupt into CMEs. Rather, whatever weak coronal loops might have been present go away 24+ hours before the CME. The extremely brilliant loops sometimes called arcades occur after the CME, and thus are effects, not causes.

The choices are that either the particles always follow the background (larger scale) magnetic field, where the field itself changes from a loop to lines streaming from the sun, or the particles flow in a small scale scale filament...

Here it would be useful to get more specific about what we're calling a background field, versus the field generated by the current itself. The environment in which CMEs occur is magnetically complex, and the Sun's dipole field has been carved up into small pieces, which approximates a quadrapole when time-averaged, but which has polarity inversions from one sunspot to the next. So I can't tell what you mean by "background" field.

In actuality, when a filament "explodes", its magnetic field vanishes.

Indeed. And this is why we need to look for causes of CMEs other than reconnection, because the magnetic field to do the work just isn't there. CMEs are actually caused by arc discharges. So it isn't magnetic reconnection, but electric reconnection, so to say (or rather, charge recombination). In my model, the significance of the disappearing magnetic field is that while the extremely powerful field surrounding a sunspot was still present, it presented a barrier against charge recombination, since electric charges moving perpendicular to that field were braked by the Lorentz force. If the field goes away, the braking goes away, charges can flow more freely, and ba-boom!

[CharlesChandler]

Speaking of resistance in the photosphere, in my model, there is a layer of negative charge inside the Sun, starting at a depth of 20 Mm, and going down to 125 Mm below the surface. The spare electrons that make up this layer were expelled from the next deeper layer by electron degeneracy pressure. That positive layer goes from a depth of 125 Mm down to 210 Mm below the surface (i.e., down to the tachocline). Then, the topmost layer is a thin positive double-layer, 20 Mm deep.

http://qdl.scs-inc.us/2ndParty/Images/C ... _1_wbg.png

As the electrons from the negative layer drift up, toward the heliosphere, they have to pass through the positive double-layer at the top. This generates ohmic heating that is the source of the heat & light that we get from the Sun.

My question is this: in the Electric Sun model, which has +ions drifting away from the Sun, what causes the ohmic heating? Sure, the migration of +ions constitutes a "current" of sorts. But just because you have a current doesn't mean that you have ohmic heating. That requires electrons skipping across atoms. If the Sun had a net positive charge, and was leaking +ions into the chromosphere, there wouldn't be any ohmic heating in the photosphere, because the spare electrons wouldn't be available for it. As best as I can tell, the Electric Sun model has charge recombination occurring in the chromosphere, once the +ions get into the voltage drop on the upper side of the hypothesized double-layer in the chromosphere. But then the heat & light that we get from the Sun would come from the chromosphere, not the photosphere.