Atmospheric Dissipation

[Soveraign]

Main Question or Discussion Point

Anyone have a link or direct info regarding the rate at which the earth's atmosphere dissipates into space? I'm looking for both an estimate of the current rate as well as a model (time and mass dependencies).

Thanks.

 

[Nommos Prime (Dogon)]

Auroral Maths

Apparently the rate of flow/energy can be calculated from the intensity of the light from the aurora australis/borealis. See below link:

http://science.nasa.gov/newhome/headlines/ast08dec98_1.htm [Broken]

 

[Mr. Robin Parsons]

Re: Auroral Maths

Originally posted by Nommos Prime (Dogon)
Apparently the rate of flow/energy can be calculated from the intensity of the light from the aurora australis/borealis. See below link:

Nice link but the outflow measurements that are given on that link are correlated to A Coronal Mass Ejection (CME) event, not to the regularity of any possible outlflow of atmosphere.

I'd suspect that there is very little "Outflow of Atmosphere" under 'normal' circumstances, cause just a little, regularily lost, would deplete the planet, in no time. (unless somehow?? replaced)

 

[russ_watters]

Its like evaporation - if the kinetic energy of a molecule is high enough that its velocity is above escape velocity (and it doesn't hit another molecule on its way out), it escapes. So at a given temperature you get a certain actual kinetic energy distribution and obviously, lighter molecules will be more likely to have the velocity they need to escape. Thats why there isn't much hydrogen in the atmosphere.

And how do you calculate that? Uh....

 

[Mr. Robin Parsons]

Originally posted by russ_watters
Its like evaporation - if the kinetic energy of a molecule is high enough that its velocity is above escape velocity (and it doesn't hit another molecule on its way out), it escapes. So at a given temperature you get a certain actual kinetic energy distribution and obviously, lighter molecules will be more likely to have the velocity they need to escape. Thats why there isn't much hydrogen in the atmosphere. And how do you calculate that? Uh....

Nigel once mentioned (in "Astro and Cosmo") that the speed of the atmosphere (molecular interactive rate) at sea level, was in the "hundreds of feet per/sec/per molecule" that would be well in excess of escape velocity, so I suspect that there are other factors at work, like the thermosphere, reductionist factors, otherwise we shouldn't even have an atmoshere left!
(but a suspicion only!)

 

[Andre]

Well, I'm not copy pasting the way to calculate that but here it is calcuted for oxygen at 25 degrees celsius: 482 m/sec average speed.

http://www.rutchem.rutgers.edu/Courses_f03/Chem161/evelecture10.pdf [Broken]

as the escape velocity on Earth is 11,000 m/sec we do not lose a lot. As all the impulses of the molecules (m*v) average out, Hydrogen gas would be 16 times faster or almost 9,000 m/sec and since this is only an average, many molecules are faster and so we can lose H2.