NASA and Government Discuss EU

[Lloyd]

Big Picture
* Since "Electric current is the rate of charge flow past a given point in an electric circuit", how is the solar wind not part of a circuit? If it weren't part of a circuit, what would cause it to move outward from the Sun and accelerate?
* See http://theory.physics.helsinki.fi/~sol_phys/Sol0609.pdf, which says as follows [my underlining].

9.2 The interplanetary magnetic field
Solar wind carries magnetic field from the Sun to the interplanetary space. This field is called the interplanetary magnetic field (IMF). It is maintained by electric currents in the expanding solar wind. While it obviously affects the local properties of the solar wind, it has also consequences on the solar rotation and on the behavior of plasma environments of solar system bodies.

* Isn't most everything that's visible in the night sky shining by electric power: plasma in glow mode and arc mode? Aren't all the filaments seen throughout the universe the visible portions of Birkeland currents that connect stars within galaxies and connect galaxies within clusters etc?
* When is plasma not part of a circuit?

[Nereid]

* Since "Electric current is the rate of charge flow past a given point in an electric circuit", how is the solar wind not part of a circuit?

First, because the solar wind is not necessarily an electric current ... you need to have a "flow of net charge", or a "net flow of charge" to have an electric current, and that generally isn't what's observed (e.g. the number of electrons and the number of protons flowing past a given point in the solar wind is the same, so no net flow - or no flow of net charge - so no current).

Second, because, in plasma physics "electric current" isn't usually defined in terms of circuits; indeed, the concept of a circuit is quite difficult to use, in general, in plasma physics.

The definition of electric current that you're using, Lloyd, is more appropriate for electric currents in wires.

[David Talbott]

The greatest challenge posed by the solar wind is the difficulty in determining whether it is entirely neutral. Certainly not entirely neutral according to electrical theorists. The oft-cited fact behind the phrase "not entirely neutral" is the unfathomable superiority of the electric force. A net drift of one particle in a million, impossible to measure, would be more than sufficient to change completely the picture of solar dynamics.

Electrical circuits in space plasma are indeed a tricky business, which is why reasonable testing of the fundamentals of the electric model will likely precede by a long shot the emergence of a an adequately quantified model. But even the plasma science pioneer Hannes Alfven did not doubt that the behavior of the Sun involved an electric circuit.

The nature of the solar circuit would be a good topic for further discussion, I'd say.

[Nereid]

The nature of the solar circuit would be a good topic for further discussion, I'd say.

I think it would be necessary to first clear up confusions/misunderstandings/etc that seem to pop up in Thunderbolts Forum threads related to the Sun, solar wind, etc - for example.

Perhaps a good place to start might be a paper (or collection of papers) that describes the fundamentals of the physics that would be used in any EU models; maybe not quite as fundamental as in this thread, but at least the parts of textbook plasma physics which are used, fundamentals not found in such, and - most important of all - clear, quantitative definitions of key terms (such as current and circuit).

[Lloyd]

Nereid said: The definition of electric current that you're using, Lloyd, is more appropriate for electric currents in wires.

* So rocks under stress produce electric currents, but we can't call them electric currents because they're not in wire?
* And we can't call lightning an electric current?
* And magnets can be made, such as the magnetic Earth, without electric currents?
* And the scientist I quoted above who said the solar wind contains electric currents isn't a real scientist?

[flyingcloud]

almost seems like a subconscious fear of electricity
could be inherent, nature or nurture?
may need it's own thread

[solrey]

First, because the solar wind is not necessarily an electric current ... you need to have a "flow of net charge", or a "net flow of charge" to have an electric current, and that generally isn't what's observed (e.g. the number of electrons and the number of protons flowing past a given point in the solar wind is the same, so no net flow - or no flow of net charge - so no current).

The solar wind has been found to be filamentary, with the filaments corresponding to supergranules in the photosphere. Filamentation in plasma is a signature of electric currents. Plasma filaments are comprised of concentric tubular current sheets. The discontinuities and turbulence between the outflowing "spaghetti like" filaments might indicate an inflowing drift current between the filaments. Each of those filaments constitutes an electric current forming a filamentary heliospheric current sheet.

Understanding Solar Wind Structure


The "spaghetti structure" of the solar-wind plasma reflects the "magnetic carpet" on the surface of the Sun, with the spaghetti in the wind being loose strands of the magnetic carpet.

“For decades we have been interpreting the spectrum of fluctuations in the solar wind as a measurement of turbulence in the wind. However, it turns out that impurities (discontinuities) in plasma dominate the signal. Hence, the spectrum is not a clean measurement of turbulence, and it may not even be a measurement of turbulence,” Borovsky said. In simpler terms, perhaps, we couldn’t see the forest for the trees.

“Because we might be misunderstanding the solar wind, we might be misunderstanding its impact on the Earth’s environment. Understanding solar wind allows us to understand the initiation and evolution of geomagnetic storms,” said Herbert Funsten, chief scientist for the International, Space & Response Division at Los Alamos.

Borovosky argues that the discontinuities are part of a structure to the solar wind that looks like spaghetti, with the discontinuities being the boundaries between adjacent noodles (magnetic tubes). In this concept, the wind plasma is structured rather than being homogeneous. He suggests that the spaghetti structure of the solar-wind plasma reflects the “magnetic carpet” on the surface of the Sun, with the spaghetti in the wind being loose strands of the magnetic carpet.

“We have also argued that the spectrum measured in the wind is a ‘remnant’ of the carpet on the Sun rather than a signature of turbulence in the wind plasma,” he says.

More on the HCS: MHD simulation of the three-dimensional structure of the heliospheric current sheet

Nereid, what say you?

cheers

[mharratsc]

So like... what I'm thinking here... is that we need to update the definition of 'electric current' a lil bit.

[Nereid]

Nereid, what say you?

A very interesting idea!

Now for the independent verification ...

In any case, it is somewhat irrelevant; the bulk motion of a plasma does not, in and of itself, constitute an electric current.

[mharratsc]

Ms. Nereid said:

In any case, it is somewhat irrelevant; the bulk motion of a plasma does not, in and of itself, constitute an electric current.

This is very true... however we're not talking about a "bulk motion of plasma" in vacuo here- we're discussing the solar wind moving past gravitationally stable objects, and a current in excess of 1,000,000 amps between the Earth and Sun alone, correct? o.O

[solrey]

In any case, it is somewhat irrelevant; the bulk motion of a plasma does not, in and of itself, constitute an electric current.

Not irrelevant because, while the bulk motion of neutral plasma doesn't necessarily constitute an electric current, field aligned current filaments and sheets do form in otherwise neutral plasma (including but not limited to) via induction and/or between regions of differing electrostatic potential which can be induced by an uneven distribution of ionizing electromagnetic radiation like microwaves and UV, or even dust. Collisions of plasma (charged particles) with neutral gas exceeding the critical ionization velocity can also produce field aligned current filaments and sheets within the "mixing zone".

The discovery of a filamentary solar wind is also in support of the prior revelation of a continuous "flux tube" (another term for field aligned current) between the Earth and the Sun.

Even our modern electronics are electrically neutral as a bulk system. Walking around with a cell phone stuck to ones head doesn't produce an electric current by the motion of the phone, nor is there any electrostatic potential between you and the phone, but inside the phone, the battery provides an internal electrostatic potential producing electric current in the conducting material of the circuitry.

cheers

[mharratsc]

Yep- I meant to say all that, too! Thanks for umm... 'clarifying' my post there, Sol! *whistles innocently*

[Nereid]

In any case, it is somewhat irrelevant; the bulk motion of a plasma does not, in and of itself, constitute an electric current.

[...] the bulk motion of neutral plasma doesn't necessarily constitute an electric current, [...]

Good, I'm glad that we agree on this point.

Good to see, too, that you have not changed the fundamental definition of "current"; otherwise you'd have turned Maxwell's equations into a mishmash of meaningless symbols ...

(I added some bold, to emphasise my original point)

[mharratsc]

We still seem to be trying to steer away from the notion that electrical currents are flowing between objects in our solar system (regardless if you wish to label it a 'circuit' or not.)

The notion that "bulk motion of plasma does not constitute an electrical current" is nowhere near as interesting- in my humble opinion- as the the very fact that electrical currents are flowing between multiple planets and moons in our solar system, and between the Earth and the Sun (if not all the planets as well)!

However, the next most pressing question in this line of inquiry to me would be: "where might we find a bulk motion of plasma <that> does not constitute an electrical current?"

[Nereid]

We still seem to be trying to steer away from the notion that electrical currents are flowing between objects in our solar system (regardless if you wish to label it a 'circuit' or not.)

If we can't agree - even in the limited discussion in this thread! - on what 'electrical currents' are, in plasmas, isn't it highly likely that any discussion of "the notion that electrical currents are flowing between objects in our solar system (regardless if you wish to label it a 'circuit' or not.)" will, sooner or later, turn into confusion, misunderstanding, and people 'talking past each other'?