Electric Venus

Historic planetary instability and catastrophe. Evidence for electrical scarring on planets and moons. Electrical events in today's solar system. Electric Earth.

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Re: "hot flow anomalies"

Unread postby glyn_collinson » Thu Mar 15, 2012 10:33 am

These were great questions!

hertz wrote: Couple of questions. I read that you borrowed some data from the Venus Express that showed the anomaly (wonder if that's what we should call them given their frequency?) happened on Mar 22, 2008. Were you able to pinpoint or even guess roughly where this happened on the surface and would surface scarring even be visible or lie buried under the atmosphere?


Hot Flow Anomalies occur in the Solar Wind outside of the bow shock, and probably would have no noticeable effect on the ground. It's possible, however, that they will cause upheavals in the upper atmosphere, or ionosphere.

hertz wrote: Is it accurate to think of these as "eddies" that get left behind, so to speak, take on a life of their own, build up an instability and then dissipate via violence? Do they always dissipate via violence?


This isn't quite what's going on. It's not really an "eddie", and I'm not sure if "instability" is the correct technical term or not. Think of them like a bubble that is attached to the bow shock.

The way that a Hot Flow Anomaly forms is basically the solar wind interacting with a planet's Bow Shock. The way we think they form is when conditions in the solar wind are just right to generate powerful electric currents that sweep the ions in the solar wind into one spot (just above the bow shock). Then it gets very hot (though processes that honestly we don't completely understand, though it's probably to do with waves). The hot plasma forms like a bubble which expands faster than the local sound speed. So, basically it's not the plasma itself that is "exploding", like a fusion bomb or something, it's this ball of heated plasma that's expanding really quickly, and deflects the incoming solar wind. This all happens really quickly, maybe less than 30 seconds, before the HFA is swept off the bow shock by the solar wind, and travels off out into interplanetary space.

hertz wrote:Given the Earth's magnetosphere, would it ever be possible for an HFA to build up to catastrophic proportions here?


Oh no no no, don't worry :) , HFAs are interesting and mysterious phenomena, but they are not at all "catastrophic". They do cause all kinds of exciting effects at the earth, like causing the whole magnetosphere to shudder (which you could detect if you had a sensitive enough compass), and cause a brightening of the Aurora, but nothing that is going to cause you any harm.

hertz wrote:Besides finding evidence for the first ever HFA on Venus, was there anything else about this project that you found particularly interesting or exciting? What, if any, is the followon to this new information, or what new projects might it spark?


Yes ;) (But I can't talk about it yet)

hertz wrote:Thanks for taking the time to be here and congrats on your find!


Well, thank you for showing an interest in my research! And every scientist always loves talking about their work :)

Do please keep the questions coming :)

~Glyn
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Re: "hot flow anomalies"

Unread postby Sparky » Thu Mar 15, 2012 12:54 pm

glyn,
The way that a Hot Flow Anomaly forms is basically the solar wind interacting with a planet's Bow Shock.


Can you explain "Bow Shock", without resorting to analogies?
We have ions moving from the sun, electric current.

There is a magnetic effect surrounding the Earth, the magnetosphere.

As I understand it, if there is an electric current, a magnetic field will be produced.

Can we assume there is then a magnetic field(s) , associated with the "current(s) " from the sun, which variably interface/interact with the Magnetosphere.

What would deform the magnetosphere, other than a more powerful magnetic field? :?

The way we think they form is when conditions in the solar wind are just right to generate powerful electric currentsthat sweep the ions in the solar wind into one spot(just above the bow shock). Then it gets very hot(though processes that honestly we don't completely understand, though it's probably to do with waves). The hot plasma forms like a bubble which expands faster than the local sound speed. So, basically it's not the plasma itself that is "exploding", like a fusion bomb or something, it's this ball of heated plasma that's expanding really quickly, and deflects the incoming solar wind. This all happens really quickly, maybe less than 30 seconds, before the HFA is swept off the bow shock by the solar wind, and travels off out into interplanetary space.


"powerful electric currents", "into one spot" concentrate, as in a z pinch!, "Then it gets very hot ", as in a z pinch!.. "-this ball of heated plasma that's expanding really quickly", as in double layers exploding! " HFA is swept off -", as a concentration of plasma, electric current, with associated magnetic field, moving with the sun's electric current and magnetic field(s)!
:D
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Re: "hot flow anomalies"

Unread postby hertz » Thu Mar 15, 2012 1:34 pm

IMO doesn't really sound like z-pinch territory, but rather "waves and turbulence," which are "ubiquitous in space and astrophysical plasmas." Currently these are some of the questions being asked:

1. How are these nearly collisionless plasmas heated by waves and turbulence?
2. What is the nature of magnetohydrodynamics (MHD) and collisionless turbulence in these plasmas, which are permeated by magnetic fields?
3. What are the dissipation mechanisms, and their roles in particle acceleration and heating?
4. What are the effects of inhomogeneity and the role of coherent structures on waves and turbulence

from here, p35: http://www.pppl.gov/conferences/2010/WO ... bFINAL.pdf
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Re: "hot flow anomalies"

Unread postby Anaconda » Thu Mar 15, 2012 2:20 pm

Hertz,

I think you are on the right course of discussion, however, I want to clarify a few issues regarding known plasma dynamic relationships -- as you probably know, Hans Alfven postulated that the electric Double Layer should be considered as an astrological object and its dynamics needed to be taken into account in those locations in space where via plasma interactions, Double Layers would form and act, both, internally within the Double Layer, itself, and upon the surrounding plasma environment.

glyn_collinson,

Thanks for participating in the forum and answering questions from forum members.

I appreciate the time and effort to do so. :)

I note the paper's abstract and, here, on this forum you do discuss electric currents and magnetic fields.

(Of course, where there are 'electric currents', there are also electric fields.)

I recognize that with particles (electrons & ions) in motion (kinetic action) some reference to fluid dynamics would be appropriate, and, in a plasma environment (which is what the interplanetary medium is) electromagnetic relationships, action, are also appropriately discussed, and, you do that.

It would seem, overall, in the abstract and, here, you rely more on mechanical analogies (fluid dynamics & kinetic dynamics of neutral particles) to expain the physical events observed & measured as opposed to the electromagnetic force and causation of ionized plasma. In the paper, from what I've read and understand, it would seem the electromagnetic force is discussed as a secondary event and causation, and, the mechanical, kinetic action, as the primary event and causation.

glyn_collinson: In terms of the paper's conclusions, how do you balance, or to put it another way, compare & contrast, the mechanical action versus the electromagnetic action, to determine what respective roles these two seperate and (sometimes complimentary, sometimes oppositional) forces have in causing, in combination, the overall physical relationships at the location observed & measured?

It would seem electromagnetic causation would be a very powerful dynamic in the studied location, dynamics, and relationships, because the Electromagnetic Force dynamic overall is the strongest of the four elemental forces of the Universe (Electromagnetic Force, Gravitational Force, Strong Nuclear Force, Weak Nuclear Force).

glyn_collinson: Does your paper recognize and discuss that where seperate bodies of plasma, with different physical properties, collide, a Double Layer will form?

glyn_collinson: If your paper does not recognize this basic plasma dynamic, why does your paper not recognize this principle of plasma dynamics?

(I apology, but I don't have access to the full paper -- perhaps I'm missing an access abillity.)

glyn_collinson: If your paper does recognize this basic plasma dynamic of the Double Layer, how does the paper take this structure & process, the Double Layer, into account and apply it to this particular location and its physical relationships?

glyn_collinson, I thank you in advance and look forward to your answers with interest.
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Re: "hot flow anomalies"

Unread postby StalkingGoogle » Thu Mar 15, 2012 7:48 pm

glyn_collinson wrote:The way that a Hot Flow Anomaly forms is basically the solar wind interacting with a planet's Bow Shock.


Do you really not understand that the "bow shock" you keep mentioning is a plasma double layer?

glyn_collinson wrote:Then it gets very hot (though processes that honestly we don't completely understand, though it's probably to do with waves).


What's more probably is you're not really measuring a "temperature" in the conventional sense, merely the energy level of a plasma, which doesn't correlate to a temperature in the sense with which we're all familiar, like degrees on a thermometer,

glyn_collinson wrote:the HFA is swept off the bow shock by the solar wind


These kinds of feeble explanations using purely mechanical analogies and ignoring the physics of plasma are what some of us have come to expect from NASA. Given that you continually and repeatedly call a plasma double layer a "bow shock" don't you think it's time you catch up a little on your education before you continue making these bald pronouncements about what's going on in space?
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Re: "hot flow anomalies"

Unread postby hertz » Fri Mar 16, 2012 6:47 am

This is an interesting question anaconda:
glyn_collinson: In terms of the paper's conclusions, how do you balance, or to put it another way, compare & contrast, the mechanical action versus the electromagnetic action, to determine what respective roles these two seperate and (sometimes complimentary, sometimes oppositional) forces have in causing, in combination, the overall physical relationships at the location observed & measured?


It seems we're often told that because plasma acts most like a fluid, that fluid dynamics are often adequate to describe its behavior, whereas here we start with the inherently electromagnetic nature of plasma and work from there. Both approaches are probably naive given the complexity of plasma, but it is always interesting to note that while virtually all mainstream articles happily use "magnetic" this or that, they rarely if ever mention the left-hand side or "electro-" part of that relationship. Wonder why? Is it taboo or something? Below is a typical example of this, which kind of leaves us here shaking our heads:

without a better understanding of how turbulent fluctuations quench or amplify mean fields, which is at the heart of the dynamo problem, it is unlikely that we will understand how the universe is magnetized
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Re: "hot flow anomalies"

Unread postby Sparky » Fri Mar 16, 2012 7:25 am

StalkingGoogle ,,
What's more probably is you're not really measuring a "temperature" in the conventional sense, merely the energy level of a plasma, which doesn't correlate to a temperature in the sense with which we're all familiar, like degrees on a thermometer,


Good point....I have no idea what they are talking about when they give millions of degrees of temperature in outer space.
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Re: "hot flow anomalies"

Unread postby glyn_collinson » Fri Mar 16, 2012 10:29 am

Sparky wrote:glyn, Can you explain "Bow Shock", without resorting to analogies?


No :P Ok, I'll start with an analogy and then go into what is actually going on, but the two are basically EXACTLY the same phenomena. Think of a supersonic jet aircraft. It is moving faster than the speed of sound, and creates a sonic boom as it travels, which is an intense pressure wave. Check out Wikipedia here http://en.wikipedia.org/wiki/Sonic_boom if you want to go into more detail on the physics of a sonic boom.

Ok, so when we talk about a "Bow Shock" in space physics, it is basically exactly the same thing, but this time the planet is stationary, and it is sitting in a flow of supersonic particles, called the solar wind. The magnetic field of the Earth is a big blunt immovable object, like a rock in a stream, and therefore a standing supersonic shock wave is generated infront of the Earth. At Venus, there is no magnetic field, but there is a thick atmosphere which the solar wind can't penetrate, so you get a similar "Bow Shock" there, albeit much smaller than at Earth, because the size of the obstacle is much smaller.

hertz wrote:IMO doesn't really sound like z-pinch territory, but rather "waves and turbulence," which are "ubiquitous in space and astrophysical plasmas."


~Glyn

Yep, bang on.

anaconda wrote:It would seem, overall, in the abstract and, here, you rely more on mechanical analogies (fluid dynamics & kinetic dynamics of neutral particles) to expain the physical events observed & measured as opposed to the electromagnetic force and causation of ionized plasma. In the paper, from what I've read and understand, it would seem the electromagnetic force is discussed as a secondary event and causation, and, the mechanical, kinetic action, as the primary event and causation.


No, the primary driver in an HFA is EM, and it's not got anything to do with neutrals. I'll get a bit more into how we think an HFA forms. However, if you really want to read the last word, check out Schwartz et al. [2000]

HFAs form on either side of a discontinuity in the solar wind, which is basically a boundary in space where the Interplanetary Magnetic Field changes direction. Picture an invisible wall in space, where on one side your magnetometer points in one direction, and when you cross it, it changes direction. These things are really common and are seen all the time.

Here, let me draw you a picture

Image

So, now, say this planar discontinuity (which are being carried along in the solar wind flow) intersects with the nose of the bow shock in such a way that the discontinuity is tangential to the shock. So in the above picture, below the discontinuity the magnetic field points into the screen, and in the upper side, the field points out of the screen. The solar wind is flowing from right to left with velocity (v).

This generates an electric field (E = -v x B)

So, if you're a proton flowing along with the solar wind, you don't see this field because you are moving with the flow. Think of a bunch of ducks on a river - from their point of view they are all stationary (velocity = 0), and it is the banks that are moving.

When the solar wind strikes the bow shock, part of it is reflected, and suddenly it is moving against the flow, and sees this huge electric field which sweeps it towards the discontinuity. So, the HFA forms along this discontinuity (which is what I meant when I said that the fields sweep the ions into one spot).

The discontinuity is swept across the bow shock, and the HFA grows until the discontinuity moves off of it...

Image
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Re: "hot flow anomalies"

Unread postby glyn_collinson » Fri Mar 16, 2012 10:39 am

Sparky wrote:Good point....I have no idea what they are talking about when they give millions of degrees of temperature in outer space.


It's the difference between "Temperature" and "Heat". Temperature is to do with the the amount of kinetic energy that the particles in the fluid have, whereas Heat is to do with how much energy a fluid can store.

So, to contrast the atlantic ocean has a very low temperature, but a very large amount of heat. The ocean can store huge amounts of energy, but if you went for a swim you'd be dead inside 4 minutes. Conversely, the ionosphere of the Earth has a REALLY high temperature (in that the particles are super energized), but it is so tenuous that it can't really store that much in the way of energy.

The fluid that you are most used to thinking about Temperature is the Earth's atmosphere. So, you know for example that a temperature of millions of degrees would absolutely incinerate you, so when you hear that space plasmas are that hot, you must think "how can that be???" It's because you are dealing with a fluid that is billions of times more tenuous than the atmosphere at sea level.

So yes, when plasma physicists talk about temperature in space plasmas, we mean the same thing that the weather man is talking about, but we are dealing with a different medium.

~Glyn
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Re: "hot flow anomalies"

Unread postby glyn_collinson » Fri Mar 16, 2012 11:07 am

Anaconda wrote:Does your paper recognize and discuss that where seperate bodies of plasma, with different physical properties, collide, a Double Layer will form?


You asked a bunch of questions about double layers, and I got so into explaining the physics of HFAs that I forgot about this comment! So, double layers form when you get areas of charge separation, so the ionosphere, for example, where the ions can penetrate further than the electrons. However, the solar wind is basically quasi-neutral (equal numbers of electrons and ions), so you won't see anything like that on large scales.

~Glyn
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Re: "hot flow anomalies"

Unread postby Sparky » Fri Mar 16, 2012 3:12 pm

glyn-, thank you for responses to my questions.

I quote you:
-the planet is stationary, and it is sitting in a flow of supersonic particles, called the solar wind.


Just a point....I can walk faster backwards than sound can travel in space! "supersonic", a poor and misleading term, as is "solar wind". The problem with analogies... :D

hertz,
IMO doesn't really sound like z-pinch territory, but rather "waves and turbulence," which are "ubiquitous in space and astrophysical plasmas."


I have to defer....but i must ask, do wave and turbulence account for the temps? :?

glyn,
HFAs form on either side of a discontinuity in the solar wind, which is basically a boundary in space where the Interplanetary Magnetic Field changes direction.----So in the above picture, below the discontinuity the magnetic field points into the screen, and in the upper side, the field points out of the screen.

What produced the magnetic fields?

When the solar wind strikes the bow shock, part of it is reflected, and suddenly it is moving against the flow,---

Do you want me to believe that particles actually bounce off of the magnetosphere, mechanically?

What reflects the solar wind? The magnetic field, correct? :D

-- and sees this huge electric field which sweeps it towards the discontinuity. So, the HFA forms along this discontinuity (which is what I meant when I said that the fields sweep the ions into one spot).


So, we have electric fields and magnetic fields? And they are concentrating ions ?!

So, double layers form when you get areas of charge separation, so the ionosphere, for example, where the ions can penetrate further than the electrons.
What observations would indicate the presence of double layers?

However, the solar wind is basically quasi-neutral (equal numbers of electrons and ions), so you won't see anything like that on large scales.


uh oh! :shock: ......... Thanks, Glyn, but i think i'll take cover in a corner... :D
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Re: "hot flow anomalies"

Unread postby nick c » Fri Mar 16, 2012 4:55 pm

hi Glyn,
Thanks for taking the time to answer our questions, it is much appreciated.
On the NASA website here, you state:
An HFA on Venus most likely acts like a vacuum, pulling up parts of the planet’s atmosphere.
Do the parts of Venus' atmosphere that get pulled up eventually recede back into the planet's atmosphere, or is there a portion that is lost or swept away by the solar wind?

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Re: "hot flow anomalies"

Unread postby glyn_collinson » Fri Mar 16, 2012 7:48 pm

sparky wrote:What produced the magnetic fields?


The sun! The solar wind has the magnetic field of the sun literally "frozen" into it, and carries it out to the edge of the solar system. It is called the "Interplanetary Magnetic Field", and is a key driver in understanding Space Weather and what's going on.

sparky wrote:So, we have electric fields and magnetic fields? And they are concentrating ions ?!

You've got it. The Electric fields generated by the interplanetary magnetic field and the motion of the solar wind plasma.

sparky wrote:What reflects the solar wind? The magnetic field, correct? :D


Yep :) You're catching on. Particles are reflected by complex phenomena like "magnetic mirroring", which it's too late at night for me to go into, and a bit off topic :)

sparky wrote:What observations would indicate the presence of double layers?


Sorry, not really my area. I've never come across them! However, the wiki entry seems pretty decent. If you're interested, then I'd start here...

http://en.wikipedia.org/wiki/Double_layer_(plasma)

sparky wrote:uh oh! :shock: ......... Thanks, Glyn, but i think i'll take cover in a corner... :D


Not sure quite what you're getting at here. But whilst you're in your corner if you're still interested in quazi-neutrality, this website goes into it in more detail...

http://www.plasma-universe.com/Quasi-neutrality


nick c wrote:hi Glyn,
Thanks for taking the time to answer our questions, it is much appreciated.
On the NASA website here, you state:
An HFA on Venus most likely acts like a vacuum, pulling up parts of the planet’s atmosphere.
Do the parts of Venus' atmosphere that get pulled up eventually recede back into the planet's atmosphere, or is there a portion that is lost or swept away by the solar wind?

Nick


Hi Nick.

That's a great question, because atmospheric loss is one of the hot topics being discussed right now in planetary science. Note that Venus has a way thicker atmosphere than we do, but the gravity is basically the same!

So, before I discuss this, it's important to note that is purely speculation at this point, because the Venus Express is the only ship there, and she can only be in one place at one time. So, all of this is an educated guess based on what we know about HFAs and Venus (but an educated guess that has been peer-reviewed :))

So, at the Earth, the ionosphere doesn't really have a specific boundary, it just expands and gets more and more tenuous. Now, it can do this because the magnetic field creates a bubble in space. However, at Venus the ionosphere has this firehose of the solar wind pouring down on it, so there is an actual measurable boundary which you can see when you cross into the ionosphere. The altitude of this is basically a pressure balance between the atmosphere pushing up, and the solar wind pressing down. The HFA deflects the solar wind, so if you are a column of ionospheric gas, suddenly the weight of the solar wind is gone and you'll want to expand upwards. In the paper I did some very rough back of the envelope calculations and it could as much as double in altitude.

Now, to make that calculation I had to make loads of assumptions, so what is really needed is some computer simulation, or further study. So, until then, I'm afraid that I can't really say any more.

~Glyn
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Re: "hot flow anomalies"

Unread postby seasmith » Fri Mar 16, 2012 9:15 pm

glyn_ wrote:

... if you're still interested in quazi-neutrality, this website goes into it in more detail...

http://www.plasma-universe.com/Quasi-neutrality


See especially third heading: Violation of quasi-neutrality, where it is stipulated
... though the containing plasma as a whole will still maintain charge neutrality, but local regions may not.

as HLF's, being energetic "local regions" almost by definition cannot be the same as
the apparent charge neutrality of a plasma overall
.
Lars Block calculated that for an idealized space charge distribution model


It must be said that hydrothermo-dynamic calculations may finally end up at the same place as electro-magnetic ones, because on a macro scale they are both barometric.
The confusion arises from the restrictive sampling mechanisms and paucity of data.
Unless someone has access to some top secret data ;) , satellites cannot portray the full interplay of terra-solar magnetospherics by sampling moving zones of charged particles and we must admit, as glyn_collinson has done,
that all of this is an educated guess based on what we know about HFAs and Venus (but an educated guess that has been peer-reviewed )


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Re: "hot flow anomalies"

Unread postby glyn_collinson » Sat Mar 17, 2012 4:59 am

Sure, quazi-neutrality is violated in "local regions", but the scale size that you are talking is on the order of about 10m in the solar wind, so for all intents and purposes, yes, you can think of it as a quazi-neutral plasma.

~Glyn
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