Hi
The Helium loss is more through interactions with infalling ions at the
magnetic poles. Helium pick-up by the solar wind has been directly
observed...
http://www.geocities.com/CapeCanaveral/Launchpad/6679/life6.html
...just scroll down a bit to the relevant section.
Thermal escape and direct action by the solar wind during magnetic field
reversals also plays a role.
Adam
PS
Look for the work of Krasnopolasky and co... Atmospheric physicists have
studied the helium loss issue for more than just our planet.
>From: Joel Duff <joelduff@nls.net>
>To: asa@calvin.edu
>Subject: atmospheric helium help
>Date: Tue, 07 Mar 2000 21:12:23 -0800
>
>Hi,
>I sent this two days ago but I never got it back and it didn't show up on
>the archive so I will try again. I am in the middle of an exchange over
>young earth evidences and one that I have been asked to respond to is the
>question of the amount of helium in the atmosphere. Well, I am quite aware
>of the typical arguments and responses but this person has included what he
>says is more current information. Not knowing the status of
>ionosphere/upper atmosphere research and this person being a physics Ph.D I
>am not sure how to respond to what he is saying her. I am hoping someone
>out there has more current information than the 1969 estimate of helium
>escape from the upper atmosphere the usual response depends upon. I have
>to admit I don't feel comfortable always falling back on just this one
>estimate of helium loss. Any advice would be greatly appreciated.
>
>Joel Duff
>
>
>Here is the relevent portion of the e-mail I wish to respond to:
>
>"+ Long agers have suggested that there must be a continual leakage of He4
>out of our atmosphere. I've been doing simulations for 4 years and find
>that ionospheric escape of He4 is very rare; in fact, I would be very
>surprised if someone could tell me how it is possible that millions of
>tons of uncharged particles can escape the atmosphere. Lighter *charged*
>particles like H+ can escape more easily. Even He+,++ and O+, though
>rare, can apparently escape. The dominant ionospheric source for the
>terrestrial magnetosphere filling is H+ (and protons). That being said,
>there is observation of heavy ions in the earth's magnetotail, near and
>distant, but it is associated with parallel to the magnetic field
>potential drops during magnetospheric substorms (e.g. Seki's paper in
>Substorms-4, Kluwer, Dordrecht, 1998, p/417). For He4 to escape our
>atmosphere requires a source of ionisation (such as during substorms
>where electrons and protons cause ionisation in the upper atmosphere.
>It would have to be a very special substorm, and even a very large
>magnetospheric storm, before these magnetospheric particles can reach so
>deep into our atmosphere that they are able to cause mass charging of
>neutral He. Then the newly ionised He++ still has to be sucked out.... Am
>I supposed to believe in miracles!?"
>
>
>
>
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