How Often Cosmic Rays?

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Westwind
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How Often Cosmic Rays?

Post by Westwind » Mon Mar 01, 2010 7:27 pm

In reading about cosmic rays, I have not been able to find any infomation about their frequency--about how often they strike the earth's atmosphere. Frequency is described as being greater at the poles than at the equator. But I haven't been able to find any numbers.

Are we constantly being bombarded by cosmic rays and sub-atomic particles? Or does it happen infrequently?

--Bill

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Re: How Often Cosmic Rays?

Post by The Code » Tue Mar 02, 2010 12:37 am

Hi Bill

I think you may need to hone in on the question. Cosmic rays means a lot of different phenomena.

http://en.wikipedia.org/wiki/Cosmic_rays

http://en.wikipedia.org/wiki/Electromagnetic_spectrum

Just a few.

Mark
Last edited by The Code on Tue Mar 02, 2010 1:13 am, edited 1 time in total.
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Chris Peterson
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Re: How Often Cosmic Rays?

Post by Chris Peterson » Tue Mar 02, 2010 1:10 am

Westwind wrote:In reading about cosmic rays, I have not been able to find any infomation about their frequency--about how often they strike the earth's atmosphere. Frequency is described as being greater at the poles than at the equator. But I haven't been able to find any numbers.

Are we constantly being bombarded by cosmic rays and sub-atomic particles? Or does it happen infrequently?
I don't have a solid quantitative answer, but I can tell you that when I'm imaging, I get a cosmic ray hit (either direct, or from the cascade of particles produced by a cosmic ray) on my approximately 1 square centimeter detector every minute or two. So we are certainly being bombarded all the time. I believe you can assume that your body is being hit at least a few times per second.
Chris

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Westwind
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Re: How Often Cosmic Rays?

Post by Westwind » Tue Mar 02, 2010 5:31 am

Mark & Chris,

Thanks for your help! I'm curious about this because when I discuss cosmic rays I think someone may ask how often we are being hit by them, etc.

I know the heliosphere blocks some cosmic rays, and the earth's magnetic field blocks some more. Some get through, however, to strike the atmosphere. It's an interesting topic.

--Bill

Westwind
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Re: How Often Cosmic Rays?

Post by Westwind » Thu Mar 04, 2010 3:18 am

I found an excellent discussion of cosmic rays on the Pierre Auger Observatory site. I would suggest this site for anyone who might be interested in cosmic rays.

It was interesting to learn that about 200 low-energy cosmic rays per second strike every square meter on earth.
This charged particle radiation comes mostly from the sun and sources inside our galaxy. Really high-power cosmic rays, however, come from outside our galaxy.

--Bill

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Amir
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Re: How Often Cosmic Rays?

Post by Amir » Fri Mar 05, 2010 2:50 pm

Hi,
Chris, i wanted to ask if you are using a CCD when you detect Cosmic Rays?
if yes, how do you recognize Cosmic Rays in your images?

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Chris Peterson
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Re: How Often Cosmic Rays?

Post by Chris Peterson » Fri Mar 05, 2010 4:59 pm

Amir wrote:Chris, i wanted to ask if you are using a CCD when you detect Cosmic Rays?
if yes, how do you recognize Cosmic Rays in your images?
Yes, they show up on CCD images. Most often they are just a single pixel or small cluster with too high a signal (often saturated). Sometimes a particle passes through the sensor at a flat angle and fills a string of adjacent pixels with electrons (which is what is happening in the image below). Sometimes a really energetic particle produces a secondary shower in or near the sensor, and that can actually look a little like a cloud chamber collision, with rays of pixels in different directions.
cosmicray.jpg
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Chris

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