The recent discussions on the Thoughts on Energy Supply thread reminded me of another cosmic balance question I have been wondering about for a while.
What is the net flow of hydrogen in or out of the Earth’s atmosphere?
As the lightest element in the atmosphere and the main component in the magnetosphere, radiation belts and magneto tail, hydrogen is constantly leaking out from the Earth. If it were not for storage in the form of water on the surface, it could have been leaking away even faster.
On the other hand the solar wind provides a constant supply of protons (ionized hydrogen) that are captured in the Earth’s magnetic field and may replenish the lost hydrogen.
I don’t know what the rates of either process are but I have looked into it enough to figure out that trying to calculate them based on simple diffusion theory, the area of the Earth or the average density of the solar wind is a gross oversimplification that could be orders of magnitude off. The hydrogen in the magnetosphere is in a plasma state and follows the complicated equations of MagnetoHydroDynamics (MHD).
But I could not find any good numbers for the net rate of hydrogen loss/accrual between the atmosphere and the magnetosphere or between the magnetosphere and interplanetary space.
Does anyone know of models that estimate these rates?
Do we even have enough info (from SOHO, WIND etc…) on the magnetosphere, the solar wind and the bow shock to develop meaningful models?
Would the rates change significantly over solar cycles or longer periods and if they did, is there any way we could measure what they were in pre-historic times?
[This message has been edited by seagull (edited November 13, 2002).]
and ask them if they could point you a reference for the ionospheric hydrogen mass flux, you might find what you are looking for.
Apparently ionospheric mass ejections due to Coronal mass ejections (CMEs), are dominated by the loss of oxygen.
Since the links I've looked at have been implying that the ratio loss of H+/O+ is being measured (among other things), the loss of H+ should be available, alas I haven't seen results published to the web.
quote: Do we even have enough info (from SOHO, WIND etc…) on the magnetosphere, the solar wind and the bow shock to develop meaningful models?
Oxygen loss has been measured extensively, and by extension hydrogen loss.
quote: Would the rates change significantly over solar cycles or longer periods and if they did, is there any way we could measure what they were in pre-historic times?
Yes, they would change. We do have proxies that track the solar cycles fairly well. I'm not sure how big a change, but I believe I read it was a bit lower historically.
[This message has been edited by LetterRip (edited November 13, 2002).]
LR, Interesting links, definitely on topic. But ...
Did you realize that most of your hits found "mass" in "Coronal Mass Ejection (CME)" which refers to the mass of hydrogen ejected from the sun rather than the mass of hydrogen (or oxygen) lost from the atmosphere?
Also, the measurements from POLAR, WIND, SOHO and GEOTAIL are spot measurements that do not even stay at the same place with respect to the cusp, bow shock, plasma sheet or magneto-tail. Every once in a while (like 1998) we get lucky and get an interesting result during a CME but I don’t know if that is enough to estimate the average net flux of hydrogen in or out of the Earth's general area.
As to the flow of O+ ions, I am not sure which link you were referring to but I wonder if it measured aurora flows from the atmosphere into the magnetosphere (that eventually come back to earth) or if the Oxygen is actually lost to interstellar space. Do CME’s give Oxygen ions enough energy to escape the Earth’s gravity well? If they do how fast does that happen?
I am pretty sure that Oxygen does not get replenished very fast by the solar wind. But on the other hand, I was not as concerned about the oxygen supply because we have quite a bit of oxygen locked in the Earth’s crust (most rocks are oxides) and the Oxygen loss rate should be at least an order of magnitude lower than that for hydrogen (based on the relative atomic weights).
It seems that this site claims there is too much Helium in the atmosphere?
quote:Such hot episodes would dispose of the helium, but note that they have not been observed.
If I am not mistaken, ion escape with help from the magnetic field could easily dominate the “Jeans Escape” mechanism that they describe (especially during magnetic storms), so I tend to be skeptical about these oversimplifications without actual calculations that show how the instantaneous rates are averaged over a longer period. Helium can spend several months diffusing to the top of the atmosphere year and then wait there for a magnetic storm to ionize a significant number of atoms to the point where they can escape with help from the magnetic field. I am not saying that this actually happens or that if it did it would be enough to account for the discrepancy they mention. But the fact that they did not even consider that option makes me skeptical about their other simplistic assumptions.
How does either side claim to know what the production rate of radiogenic Helium is or how fast it diffuses out of the crust?
quote: The rate at which helium is entering the atmosphere from radioactive decay is known fairly well; as is the rate at which helium is presently escaping from the atmosphere into interplanetary space.
Their references are not links that I can follow and check. Posts: 1910 | Registered: May 2002
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Ok, Link1 pretty much says the same thing I did above. Since I came up with it in a few minutes with no supporting information, I don;t trust my own argument that much, and I don;t see why I should trust theirs.
Bottom line, we are back where we started.
I suspect that we are still a few decades away from actually having enough space measurements to make a meaningful model of the atmospheric balance. Do any of your links show otherwise? Most of them seem to argue for or against the young Earth theory and to use copious references as an appeal to authority without actually giving any meaningful info.
What is wrong with simply saying: I/we/scientists don't know (yet)?
[This message has been edited by seagull (edited November 13, 2002).]
This link suggests that hydrogen escape was much higher historically, corrected link
The reason the links were for/against a particular view is that the first site was a YE creationist site, the other links were fro m talk.origins. I posted the YE site, because it was what I'd stumbled across before I had to leave and raised the interesting question I'd not heard before on helium balance...
Edit - corrected the link to point at the correct article for the second link
[This message has been edited by LetterRip (edited November 16, 2002).]
While the first link examined Venus, the situations are similar enough that the equations given apply to Earth as well.
It also gives the empirical number for earth (it was in a unitless ratio, but the units are later given for the top number, which gives us the units for the bottom number... I'll find it here in a bit)
The link I'd meant to put was from NASA, essentially what it said was that bacteria preferentially produced methane in Earth prehistory, this resulted in a much higher historical loss rate for hydrogen.
quote: Only a small portion of between 0.6 and 1.6 *10^12 g/yr enters the stratosphere.
The H2-content of stratosphere and mesosphere amounts to about 30*10^12 g with a strongly varying life time of between 1 and 100 years (depending on chemical composition and temperature). Measurements of the isotopic composition indicate that the hydrogen and water vapour of the upper stratosphere result mostly from hydrocarbon decomposition, not from tropospheric diffusion of H2 or H2O .
In a height of 40 - 80 km the decomposition H2 + OH -> H2O + H is the dominant destruction mechanism. Above 140 km atomic hydrogen remains the most abundant chemical "compound" where a loss flux of between 16 - 31 *10^7 particles/cm2 is calculated from experimental data .
 S.C. Liu, T.M. Donahue, Realistic model of hydrogen constituents in the lower atmosphere and escape flux from the upper atmosphere, J. Atmos. Sciences 31, (1974), 2238 - 2242 http://www.hydrogen.org/Wissen/Vapour.htm