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Author Topic: How do cosmic ray particles reach the ground?  (Read 3019 times)

Johann Mahne

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How do cosmic ray particles reach the ground?
« on: 03/08/2011 17:32:57 »
If cosmic rays are made up of atomic particles how do they penetrate through the atmosphere without being absorbed?


 

Offline Geezer

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How do cosmic ray particles reach the ground?
« Reply #1 on: 03/08/2011 19:05:10 »
Good question, and you got the answer right too. They don't penetrate the atmosphere. They interact with molecules in the atmosphere which converts them into less energetic particles.
 

Offline CliffordK

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How do cosmic ray particles reach the ground?
« Reply #2 on: 03/08/2011 20:07:15 »
I think Geezer is right.  The majority of particles from the solar wind and cosmic rays are absorbed in the upper atmosphere, after which they mix with the rest of the atmosphere, and eventually reach the surface.

Thus, they can replenish supplies of Tritium and Carbon-14 on the planet's surface.

There are theories that cosmic rays affect ocean evaporation.  But, I believe these are relatively weak theories.
 

Offline terrildactl

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How do cosmic ray particles reach the ground?
« Reply #3 on: 26/11/2011 17:28:42 »
Most of this is bounced away by the Earths magnetosphere, I dont think they can be absorbed, they even slowly make their way completly through the earth, and onwards. Yes there is much inter action between stratosphere,and troposphere.
 

Offline yor_on

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How do cosmic ray particles reach the ground?
« Reply #4 on: 26/11/2011 17:42:48 »
Are you thinking of neutrinos Terrildactl?

When I read it, it made me think of 'muons' :)

"Cosmic ray muons make up something like half of the natural sea-level radiation background. They are produced high in our atmosphere from the interactions of primary cosmic ray particles with atmospheric gas nuclei. The muons then lose energy as they pass through the atmosphere to reach us. Some will lose so much energy that they fail to reach us and, as a result, there is a dependence of the muon rate on the atmospheric pressure.

The primary cosmic rays reach the Earth after travelling through the solar wind. Not all of them are able to make that journey, especially when there are strong solar outbursts. As a result, the rate of detection of muons depends on the "solar weather" and, at times of solar flare activity, there may be significant changes to the muon rate known as "Forbush decreases". These are naturally more common at times of maximum solar activity which follow an eleven year cycle. Solar activity is currently building towards the next maximum, expected in the year 2000.

The muon detector is located in the Physics Department of the University of Adelaide with about 300 g cm-2 of building material above it. Our atmosphere has a depth of about 1000 g cm-2 so, assuming that muons lose energy by ionisation at a rate of about 2 MeV(g cm-2)-1, the threshold energy (at production) for the muons we detect is a rather high 2.6 GeV. To get lower energies, neutron monitors are used since neutrons do not suffer ionisation energy loss in passing through our atmosphere. The Earth's magnetic field prevents low energy charged cosmic rays from reaching the atmosphere. There is a rigidity threshold for all place on the Earth due to this. For Adelaide it is about 3 GV. By coincidence then, for protons, this is about the same value as the threshold for muons to reach the detector." From Cosmic Ray Muon Detector.


 

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How do cosmic ray particles reach the ground?
« Reply #4 on: 26/11/2011 17:42:48 »

 

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