Who cares about Earth's magnetic field and ozone layer?

[mugaliens]

Could someone please help me worry?

Reversal average roughly ever 300,000 years, though they vary from tens of thousands to many millions of years.

Not only are they not correllated with extinction events, our ancesters have lived through many of them, so why are you worried?

I'm sorry, but I can't help you worry - at all, at least not about magnetic reversals.

As for the ozone hole, that's clearing up now, and some evidence exists the CFCs had little to do with it, so I can't help you worry about that one, either.

 

[Jon Richfield]

Jon, I'm afraid I didn't read your post because it stunk of something horrid.
Rest assured I will not be commenting further on anything you have to say.

Well Bill, I cannot fault you on your assurance, for sure! What a contrast with a certain other very recent respondent, who had the interest and helpful impulse to make a courteous proposal, and the grace to concede that he was not in a position to refute an objection to that proposal. He did not refuse to read the material when he found that it errr... stunk of something as horrid as a sceptical reception.
Far be it from me to demand that you waste your time on defending the indefensible, but don't let me inhibit you from a few night thoughts on topics such as re-evaluation of your own ideas in the face of friendly, but factual discussion of deficiencies in their validity.
Have fun!
Jon

 

[jreelawg]

I think conciseness is actually key, as opposed to extensiveness in the pursuit of answers to your questions.

You do well to be extensive, and show an understanding what we know about simplified direct interactions related to the topic. However, the point you are missing, is that the actual interactions in it's actual extensive form, and the effect long and short term, range from being poorly understood by science, to impossible to predict given this understanding.

In other words, rather than being incredibly elaborate using shallow assumptions, it is easier to concisely review what observational evidence there is to offer, and from that theorize humbly what you can from it.

This is where the truism you refer to comes from isn't it. I agree that truism is annoying. I find this especially true of even more illusive subjects such as theoretical cosmology.

But in the case of Earth's magnetic field, we do have some evidence from which to spin a theoretical web of assumptions. I hope you are not arrogant enough to be so sure things would be fine and dandy without a magnetic field, or ozone layer.

If you can't tell yet, you are falling into the same hocus pocus you show such distaste for in your assumptions.

If you want to understand why scientists theorize what they do about the magnetic field of earth, then you should start by researching the category of observation, and then evaluate on an individual basis the leading theoretical work based on it.

Nobody here is going to post anything which can replace literature and data on the subject, which may take some time and patients to work through, and there is no guarantee that you will have the intelligence to understand it deeply enough to be critical of it.

But since you probably don't have that kind of time on your hands anyways, you have fun playing a game of wit and sarcasm with some people on a forum, and with such a shallow approach, your words are of little value. It you don't trust the work of others we take for grant it, then let's hear some thoughts about specific work, and how you think it is flawed.

Once we have some more solid ground to tread on, maybe you can get us somewhere.

 

[Jon Richfield]

You do well to be extensive, and show an understanding what we know about simplified direct interactions related to the topic. However, the point you are missing, is that the actual interactions in it's actual extensive form, and the effect long and short term, range from being poorly understood by science, to impossible to predict given this understanding.
In other words, rather than being incredibly elaborate using shallow assumptions, it is easier to concisely review what observational evidence there is to offer, and from that theorize humbly what you can from it.

Jree, Some of your points have merit, and I hope that you will not substantiate the impression you give, of an uncomfortable level of impatience with the tone that this thread has developed. The questions that I have posed are perfectly serious, and quite important (as you imply in some of your own reactions) and if any person undertaking to respond sees fit to cover the emotional and intellectual inadequacies with a high tone in lieu of substance, then he has no one better to blame than myself for permitting him to show himself up.
I am sorry if you have seen this as the point of the exchanges with certain persons who just recently criticised my prolixity in making meaningful statements, while replying to them at only slightly less length, but far lower content. Still lower content would have been much better, giving the yet lower factual and logical accuracy he displayed.
Notice that at least one other participant, without raising temperatures or any need for discourtesy in any form whatsoever was comfortably able to present a suggestion and on reflection, to retract it.
You appear to suggest that it is easier to put matters concisely than extensively. If that is the case with you, then please accept my envious admiration. Personally I side with Pascal, who famously, and with many emulators, apologised for not having time to produce a more concise communication.
If you really think that it is easier to produce concise observations on what "observational evidence there is to offer" (not to mention its adequacy) as a basis for humble theorisation, please set the example. In doing so, please bear in mind that I had begun by explaining that I had in fact been reading fairly wide ranges of material explaining why horrible things would happen as soon as our magnetosphere collapsed, disappeared, attenuated, shifted, or whatever option individual authors, palaeontologists, geophysicists and the like supported. Having done so I humbly theorise that the effect would be comparatively trivial in the event of a magnetic polar inversion, and even wonder whether it would be very important if the field vanished completely.
If you should happen to suspect that I am trolling the forum, I can only request, assuming that you have the time to read what I write, that you match your courtesy to the level that you urge on me, and read what I write, taking it at face value, rather than reading either undue ignorance or ill faith into whatever I said.

So, may I propose that we treat each other with the reciprocal respect that, as a rule, I find most comfortable in correspondence? I hope you don't mind seeing your way to such a relationship. Most of the people in forum show no difficulty in doing so.
And now:

But in the case of Earth's magnetic field, we do have some evidence from which to spin a theoretical web of assumptions. I hope you are not arrogant enough to be so sure things would be fine and dandy without a magnetic field, or ozone layer.

If I did, would I be asking the question? The material that I have read to date, suggesting Intimations of Universal Disaster have come from diverse sources, some very highly placed. This however is a matter of science, not of authority. In science, as I am sure you are properly aware, authority has its place, but not as a substitute for conviction or logic. I am sure that you, given your apparent background, would refuse to let yourself be persuaded or bullied into accepting as substantial fact, something that plainly is based on non-cogent observation and inadequate logic.
And that Sir, is how it is with me. It is not a matter of nailing my colours to a mast; there is no mast. I rather take the attitude of Keynes, who said: "When the facts change, I change my mind Sir. What do you do?"
Now, no doubt you have read my original question, in which I pointed out the very limited protective role played by our magnetosphere. Do you deny any of the factual statements that I made or quoted in asking that question? If so, please give me a hint.
Similarly do you deny my deductions concerning the probable effects at ground level? If so I promise you that I would be delighted to be corrected. Would you even, quite reasonably pointing out that there are limits to our factual knowledge of the field, so that you could hardly be expected to produce any rock solid pronouncements, simply make some reasonable suggestions as to why my optimism (such as it is) might be seen as excessive?

Do my expectations and requests seem unreasonable in context? Or too arrogant in context? I remarked somewhere that I would be very interested to see the effects of a magnetic pole inversion, and that certainly is true. I also am of the opinion that the effects would be nothing like as dire as it is fashionable to prognosticate, but at the same time, I have not the slightest doubt that there would be untoward consequences as yet unforeseen (certainly by me, but I invite you to propose any that strike you as salient. Only please spare me the skin cancer and shortened lifetime horror stories purveyed by certain parties in forum!)
All of which said, if you were to give me a magic button which I could press to invert our planetary polarity, of course I would refuse to press it! What was there in my question to suggest anything less?

If you want to understand why scientists theorize what they do about the magnetic field of earth, then you should start by researching the category of observation, and then evaluate on an individual basis the leading theoretical work based on it.

For example? Which salient points do I seem to have been pressing in contradiction to the physics, geophysics, and astronomical physics of the past two centuries or so? Remember: I spoke in terms of the implications for uncharged particles, cosmic rays, and solar wind. I also spoke in terms of mainly the charged particles in the solar wind and low energy cosmic rays. I spoke furthermore in terms of the differences in effect on various parts of the planet and various levels in the atmosphere.
Any problems so far?
Anything crucial that I seem to you to have omitted? Please do not hesitate to particularise; I sincerely assure you of my gratitude for anything you should see fit to contribute.
That is the sort of thing for which I ask the question.

Nobody here is going to post anything which can replace literature and data on the subject, which may take some time and patients to work through, and there is no guarantee that you will have the intelligence to understand it deeply enough to be critical of it.

Really Jree! REALLY!

I shall charitably assume that you mean that strictly in the Pickwickian sense. If I did otherwise, I should have to assume that you had undervalued the scope of the good sense, patience, good nature, and erudition of the community online. And as for intelligence...
I also would have to assume a gross misunderstanding on your part, of the function of such a forum as this. It is not a substitute for an education, but a tool, a resource for the educated mind. It exposes one not only to a wide range of general and specific knowledge, but to helpful opinion and discussion. In some contexts it helps one get down to the real basics and nitty-gritty, whether theoretical or empirical, whereas in many other contexts it tells one all one needs know, or is equipped to know of a field at a far more superficial level (the handwaving, Bohr atom, Schrodinger's cat level). You would hardly believe this, but on a few occasions I have done some helpful handwaving myself!
Fair exchange and all that...

But since you probably don't have that kind of time on your hands anyways, you have fun playing a game of wit and sarcasm with some people on a forum, and with such a shallow approach, your words are of little value. It you don't trust the work of others we take for grant it, then let's hear some thoughts about specific work, and how you think it is flawed.
Once we have some more solid ground to tread on, maybe you can get us somewhere.

Now now, Jree! You are not supposed to show your temper before you have established your position as an appropriate authority. In this case YOU accuse ME of, what was it again? Oh yes: having "fun playing a game of wit and sarcasm with some people on a forum, and with such a shallow approach". And this in the face of my having pointed out the implications of the poor penetration of the particles in question in our atmosphere, and the trajectories of charged particles in the magnetosphere? Where have you seen any work to deny these simple facts? Some of them go back to the days of Tyndall and Faraday, never mind Rutherford! Most of them are schoolwork today, rather than university curriculum! (Well, I certainly first encountered them at school...)

Which of them are too shallow for you? Which deeper insights doom us as soon as the magnetosphere dips or falters? I could hardly think of anything more solid than:
People in influential positions have expressed fears of ionising hazards if our magnetosphere flags.
This seems implausible in the light of the nature of the atmosphere.
Could someone please point out some flaws in the basis of my scepticism?

Well, Jree?

Over to you. It seems that you have the replies all cut and dried.

Cheers,

Jon

 

[Jon Richfield]

There was a reply from Billiards in my notifications, but I seem unable to find it on line. I trust that he will forgive me for working from the notification instead of the forum entry.

1. My apologies for calling you Bill. It was not intended to represent your name, but as an abbreviation for Billiards. I am sorry if the abbreviation gave offence. In future I shall spell it out to avoid unnecessary bile or bickering.
2. "The magnetosphere does in fact deflect high energy particles from equatorial regions."
This is a very interesting assertion and deserves some amplification. I hope you (or anyone else in forum) will be willing to expand on it, even if we only consider charged particles. Trivially, any charged particle not traveling parallel to the "lines of force" (an equally trivial concept that we might as well neglect in practice) will be deflected by a magnetic field in the sense that its path will be altered. However, it does not follow that it will be deflected in a mode and to a degree that will protect whatever lies below. For example, a TeV or PeV particle would hardly notice our magnetosphere, whereas the typical solar wind particle is hardly "high energy"; if it were deflected it would in due course wind up either in a van Allen belt or at a pole, or perhaps in the atmosphere, where it would rapidly thermalise. Now, suppose that some charged particle does escape the clutches of the magnetosphere, or that the magnetosphere vanishes; how far might we expect it to penetrate the atmosphere with any significant energy excess at all? It might be instructive to consider as an illustrative example, the altitude to which the aurorae descend before they peter out. So far Billiards, this does not seem to suggest much increase in hazard to equatorial inhabitants, beyond what the atmosphere can handle very comfortably. But the whole reason for this thread, please remember, was to find out what I had overlooked or misunderstood. Please contribute! Mugaliens wasn't much help; expects me to do all the worrying myself! <mttr mttr!>

Meanwhile, all the best!

Jon

 

[Ophiolite]

Jon,
you suggested somewhere above that the loss of the magnetosphere may not cause any problems. There is one that immediately springs to mind: atmospheric erosion by the solar wind. This is a very real phenomenon. It is probably the primary cause for the low atmospheric pressure on Mars. I suspect there would be other deleterious effects though I share with you the belief that the doomsayers are greatly exagerating these.

One point no one seems to have brought out is that during a pole switch there is no point at which the field disappears entirely, it simply weakens and becomes more complex.

 

[billiards]

There was a reply from Billiards in my notifications, but I seem unable to find it on line. I trust that he will forgive me for working from the notification instead of the forum entry.

1. My apologies for calling you Bill. It was not intended to represent your name, but as an abbreviation for Billiards. I am sorry if the abbreviation gave offence. In future I shall spell it out to avoid unnecessary bile or bickering.
2. "The magnetosphere does in fact deflect high energy particles from equatorial regions."
This is a very interesting assertion and deserves some amplification. I hope you (or anyone else in forum) will be willing to expand on it, even if we only consider charged particles. Trivially, any charged particle not traveling parallel to the "lines of force" (an equally trivial concept that we might as well neglect in practice) will be deflected by a magnetic field in the sense that its path will be altered. However, it does not follow that it will be deflected in a mode and to a degree that will protect whatever lies below. For example, a TeV or PeV particle would hardly notice our magnetosphere, whereas the typical solar wind particle is hardly "high energy"; if it were deflected it would in due course wind up either in a van Allen belt or at a pole, or perhaps in the atmosphere, where it would rapidly thermalise. Now, suppose that some charged particle does escape the clutches of the magnetosphere, or that the magnetosphere vanishes; how far might we expect it to penetrate the atmosphere with any significant energy excess at all? It might be instructive to consider as an illustrative example, the altitude to which the aurorae descend before they peter out. So far Billiards, this does not seem to suggest much increase in hazard to equatorial inhabitants, beyond what the atmosphere can handle very comfortably. But the whole reason for this thread, please remember, was to find out what I had overlooked or misunderstood. Please contribute! Mugaliens wasn't much help; expects me to do all the worrying myself! <mttr mttr!>

Meanwhile, all the best!

Jon

Yes there was a reply from me but I deleted it. The reason it was deleted is because it did not add any value to the thread and I felt it was better to get rid of it before it became entangled. I was in merry spirits when I made that post, and it was a rather crude, egregious, satirical dig at you posting style, which I later regretted when I started to sobre up. Anyhow, it looks like you read it, and I apologise, but I am glad that it does not seem to have caused you offense.

I do prefer Billiards to Bill, but that was not the thing that caused offense.

Now that I read more of your posts I think I "get them" more. When I first read them they read like snide personal attacks delivered in an arrogant condescending way, but actually on second anlaysis I find them to be the ramblings of a curious, sharp mind with a slightly odd sense of humour, and little concern for charm (that's just my personal interpretation -- and it means nothing more, or less, than that -- no doubt I am completely wong!). As you can probably tell, I am not an obsequious person, and I have little concern for charm (unless you're my girlfriend's parents!) I am also lazier than the average poster here in that I refuse to trawl through the net to find evidence which will make/refute someone else's point -- unless it happens to overlap with my own personal interests and I happen to be in a good mood.

Anyway, enough of that, I am ready to move on..

 

[billiards]

Jon,

I agree that the atmosphere will protect us from the solar wind, with or without a magnetic field.

There is the issue of atmospheric stripping, but my reading around has not shown this to be hugely significant.

Without a either a magnetic field or an atmosphere the solar wind would be damaging to us. Low energy electrons can damage DNA. http://iopscience.iop.org/1402-4896/68/5/N03;jsessionid=C1CB1D055D481E81E6A69707D2EB86D8.c2

The magnetic field would protect us if there were no atmosphere (ignoring the absurtity of living on a planet without an atmosphere).

I said earlier that I am not obsequious -- but this has been interesting, and I am glad you gave me reason to do a little reading -- for that I am grateful. Next time a lecturer warns of the dangers of losing the magnetic field, I will make sure to raise a few questions, and hopefully learn a little more.

I will share thi website which I found to be quite informative: http://www.phy6.org/Education/index.html

 

[Jon Richfield]

you suggested somewhere above that the loss of the magnetosphere may not cause any problems. There is one that immediately springs to mind: atmospheric erosion by the solar wind. This is a very real phenomenon. It is probably the primary cause for the low atmospheric pressure on Mars. I suspect there would be other deleterious effects though I share with you the belief that the doomsayers are greatly exagerating these.

One point no one seems to have brought out is that during a pole switch there is no point at which the field disappears entirely, it simply weakens and becomes more complex.

Thanks Ophiolite.
I agree that the ablation of the atmosphere is (to my eye at least) the most substantial concern in the event of loss of the magnetosphere. I am however, still a little sceptical of that as well.
See, (in the light of recent castigation of my tendency to neglect citation at the refereed publication level, I am hesitant to make hard assertions) it seems to me that in the absence of a magnetosphere there should be solar wind particles of three kinds from this point of view: Those that miss us completely, those that hit us (our atmosphere anyway) directly, and those that skim the atmosphere and knock atmospheric particles into escape trajectories. So far, so mundane, right? So let us ignore the first class, as being essentially irrelevant.
Next, consider the particles that "hit us directly". These are particles of whatever energy, that do not strike the atmosphere tangentially. They will generally, whatever transient ionic states they may assume, end up as components of atmospheric molecules, whether hydrogen, water, ammonia or the like. All right, some metals also might arrive, eventually becoming part of the Earth's crust or the biosphere, but they would be in the vanishing minority. In general, refer to all these particles as accreting.
In short nearly all such particles would contribute either to the atmosphere or the hydrosphere.
Finally let us consider those that I might call tangential impactors. By this I mean that they are not quenched in the atmosphere, but remain in space and each takes at least one atmospheric particle with them.
For current purposes, I propose that any molecules of water be regarded as part of the atmosphere (unless you think of serious logical objections).
Now, obviously this reduces the problem to a comparison between the rates of ablation and accretion. That sounds very simple, but as you will recognise (probably well ahead of me) there is no way to tell from first principles which of the two is greater, and by how much. If I were to guess, I should expect accretion to reign, but I could not defend the idea with any confidence. What is more, I could not even argue very strongly for the net rate of ablation to be very low. The fact that Mars and Mercury are nearly without atmosphere hardly figures, because Venus, with its negligible magnetosphere, has a very nice atmosphere, thank you, and it is between the two in its orbit round the sun.
Frankly, I would hate to bet whether a billion years without magnetosphere would cause us to run much short of air, but I am perfectly aware that I am in no position to defend the position very strongly, only that the area of interception of accretion material exceeds the area of ablation, and the conditions for accretion of a particle are far less demanding than for ablation.

You are right of course, about the state of the magnetosphere during the switch, but I have no idea whether the effect will differ significantly from a negligible magnetosphere.

Comments welcome, as always!

Cheers,

Jon

 

[Jon Richfield]

There is the issue of atmospheric stripping, but my reading around has not shown this to be hugely significant.

Thanks. This is consistent with my impressions, but as I said to Ophiolite, I am hugely uncertain.

Without a either a magnetic field or an atmosphere the solar wind would be damaging to us. Low energy electrons can damage DNA.

Fairly low, anyway! I must say I was slightly surprised by the 3 eV figure!
But my rejection of that risk was rather because I reckoned that the tissue penetration of free, thermalised electrons would be trivial.

The magnetic field would protect us if there were no atmosphere (ignoring the absurtity of living on a planet without an atmosphere).

I said earlier that I am not obsequious -- but this has been interesting, and I am glad you gave me reason to do a little reading -- for that I am grateful. Next time a lecturer warns of the dangers of losing the magnetic field, I will make sure to raise a few questions, and hopefully learn a little more.

Billiards, I can hardly say how much I appreciate your generosity and courtesy in reacting in this way to a difficult situation. No one knows better than I that it is far harder to mend a bad atmosphere than to establish a good one. I admire your positive attitude and envy the lecturer, should your anticipated warnings and questions materialise. I always have appreciated class members who have gone intelligently beyond the prescribed work. A word to the wise though: if the lecturer loses his cool, let it go! Hell hath many furies like unto the Politically Correct when their views are called, however reasonably and sweetly, in question. But even those furies are not kept in Hell for nothing!

I will share thi website which I found to be quite informative: http://www.phy6.org/Education/index.html

Thanks; looks like a nice site. I'll fossick around a bit.

All the best,

Jon

 

[Ophiolite]

Jon,
you are trying to assess the impact of the solar wind on our atmosphere through logic. I prefer to look at the facts.

You mention that Venus has retained a thick atmosphere despite having no magnetic field. However consider this research. I have emboldened the central point.

Zhang,T.L. et al Little or no solar wind enters Venus' atmosphere at solar minimum, Nature, Volume 450, Issue 7170, pp. 654-656 (2007).
Abstract

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere2,3. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum.

The strength of this interaction (induced field) I understand to be due to the thickness of the Venusian atmosphere, so one would not expect the same reaction were the Earth to lose its field.

 

[Jon Richfield]

Jon,
you are trying to assess the impact of the solar wind on our atmosphere through logic. I prefer to look at the facts.

You mention that Venus has retained a thick atmosphere despite having no magnetic field. However consider this research. I have emboldened the central point.

Zhang,T.L. et al Little or no solar wind enters Venus' atmosphere at solar minimum, Nature, Volume 450, Issue 7170, pp. 654-656 (2007).
Abstract

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere2,3. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum.

The strength of this interaction (induced field) I understand to be due to the thickness of the Venusian atmosphere, so one would not expect the same reaction were the Earth to lose its field.

Thanks Ophiolite, there is some interesting material there. I did some following up and came away with deeper reservations than ever. Consider the following quote from:
www.lpi.usra.edu/meetings/lpsc2009/pdf/1408.pdf.
"The magnetic field of the solar wind can both act as a shield and as a facilitator for removal of the atmosphere. The magnetic field piles up on the forward side of Venus and creates an obstacle to the flow."
If nothing else, the hits I found supported your preference for empirical evidence, which was in various ways very ambiguous. (Let's leave the concept of "facts" to the metaphysicians shall we!)

I do take your point about the difference between the thickness of the atmospheres of Earth and Venus, but I think you would agree that the nature of its influence is not unambiguous, magnetic field or not.
Now, one of the sources I found estimated the rate of loss of Venusian atmosphere under the influence of the solar wind at roughly 1e25 ions/sec. That seems to me to approximate 1 kg/s or thereabouts, which amounts to about 1e4.5 tonnes/Y. Given the Earths atmosphere at about 1e15.5 tonnes, and that of Venus being about 100 times more, it seems that Venus could stand that rate of leakage for some 1e13 years. Whether to extrapolate that to Earth at 1e11Y, I do not know, but let's assume that we could afford to lose 10% of our atmosphere if our magnetosphere vanished. That would should take us something like 1e10Y, which is roughly twice the current age of the planet, and over two thirds the estimated time since the big bang.
Please check my figures for reasonability and accuracy, assuming that my sources are at least reasonably sound. I am of course assuming a spherical herd of spherical cows, but if you know where to find square cows in this particular pasture, do tell!
Of course, neither logic nor empirical data are adequate at this stage of play, so not a word I say is to be taken very seriously. In fact, it is by no means clear to me why at present we should be terribly sure whether the magnetosphere isn't increasing our net rate of leakage. In the case of Venus for example, it seems that most of the losses are via the magnetotail, with extremely low penetration of the bulk of the atmosphere at solar minimum. If there were no magnetic shielding as a result of the interaction with the solar wind, Venus might be gaining atmospheric material from the solar wind.
I do not urge that as a prospect of course, but it seems no less reasonable than some other proposals.
Be all that as it may, if the back of my envelope isn't in desperate need of a new battery, I think I'll shunt my concerns over the rate of atmospheric ablation in the event of total loss of magnetosphere, firmly to the back burner!
Thanks for that material. Very illuminating. Billiards dropped a hint that the losses might not be very impressive, and I feel better and better about having raised the question in general. I am grateful to all you chaps for your contributions (even Mugalien's failure to worry me!)
Now all we need is a totally new contribution to turn up a totally new aspect to the topic.
Any bets anyone?
Cheers,

Jon

 

[billiards]

Atmospheric stripping by the solar wind on Venus preferentially strips helium, hydrogen, and oxygen.

This may be the critical observation in understanding why Venus is so dry today. Perhaps the solar wind has gradually stripped the planet of water.

http://www.esa.int/esaMI/Venus_Express/SEM0G373R8F_0.html

(The findings appear in the 29 November issue of the scientific journal Nature, in the paper: 'Venus loses its water through the plasma wake', by S.Barabash et al..)

The point is, perhaps the magnetosphere is important to us (and all life) here on Earth, as it has stopped our planet from drying up...?

 

[Andre]

Considering this interaction of the Venus atmosphere and losing water, the pre-supposition here is that the current condition is steady state for (most of) the existence of the planet, i.g. many billiards years.

However, if the genesis of the planet resembled that or Earth, having roughly comparable distributions of the elements, one would observe that the amount of carbon in the Venus atmosphere is close to the same order of magnitude of the total estimate amount of carbon on earth. But how did all that carbon get in the atmosphere?

So how about the total amount oxygen? We could not dismiss the amount of oxygen in the CO2 of the Venus atmosphere compared to the total amount of oxygen of the planet, could we? So is it far fetched to presume that the some oxygen in the atmosphere has been in the water of Venus previously?

So again, why that dense CO2 atmosphere? Given the geological past of the planet, with the assumed http://web.mit.edu/newsoffice/2010/venus-mapping-0322.html, could it be that this dense atmosphere is the result of those processes, i.g. outgassing and burning most of the carbon that used to be in the lithosphere?

Also if Venus was an eartlike rotating planet in the past (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-48FCD2X-1&_user=10&_coverDate=05%2F31%2F2003&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1522070522&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=94776a570ffe3d63a9b821422f4fa1c9&searchtype=a) could it be that it had a magnetic field at that time?

But the point is that Venus was likely completely different in the past, so you can't draw conclusions from present states, assuming that it was equal in the past.

 

[Jon Richfield]

Atmospheric stripping by the solar wind on Venus preferentially strips helium, hydrogen, and oxygen...

The point is, perhaps the magnetosphere is important to us (and all life) here on Earth, as it has stopped our planet from drying up...?

Fair enough billiards, but even if this were the start of our permanent loss of any terrestrial magnetic field (which is of course possible, though no one has been seriously arguing it afaik) it seems as though we are talking about GY orders of magnitude before things were likely to get really tight.

Now, as some of you might well know, I am inclined to take a long view about worrying about things, but so far this does not look like something to worry about yet. If the actual period of negligible magnetic field is to be mere millennia every MY or so, then we had better worry about our sun going red giant first.

Gee... yeah...

Jon