# Why cosmic ray intensity needs correction with pressure?

1. Nov 25, 2012

### sctheorist

Hi guys,
I cannot understand why we need to correct cosray intensity with pressure and why the equation that describes the phenomenon is I=Io*exp(-a(Δp))? I want to know the phsyical meaning of this(i assume,experimental) result...

Thank you...

2. Nov 25, 2012

### Staff: Mentor

More context would help.
A correction where, and depending on which pressure?

3. Nov 25, 2012

### sctheorist

By pressure I mean the atmospheric pressure above the neutron monitor for example..The exact equation is:

I=Io*exp(-a(Pi-Pm)) where:

I=corrected with pressure intensity of cosray
Io=the intensity recorded by the neutron monitor
a= constant(namely the pressure coefficient)
Pi=the atm. pressure at the time of measurment
Po=the mean value of pressure in a particular amplitude where the measurment is taken

thanks...

4. Nov 25, 2012

Staff Emeritus
The higher the pressure, the more material (air) is above you and the fewer cosmic rays get through.

5. Nov 25, 2012

### sctheorist

if the pressure is Pi>Pm then the argument in the exp is negative(a is positive) and exp(-a(Pi-Pm) is less than 1.So the corrected value I is less than the recorded Io,which doesn't make sense. In high pressure you supposed to record a value i.e. Io=40 and the correction should be I>Io because high pressure prevents you to count all events available,right?That's a contadiction if I am not wrong...

6. Nov 25, 2012

Staff Emeritus
Look, sctheorist (why so rude?) the sign of the correction depends on the sign of a.

7. Nov 26, 2012

### sctheorist

No no you misunderstood my friend...I used "look"' in a friendly manner..Maybe it's because I'm not american..Seriously I didn't mean to offend you or something..In my language this phrase has a different meaning..Anyway...

I had a thought today about that..Maybe it has something to do with the equation I=Io*exp(-μχ) that refers to an absorber above your detector. χ being the length of the path within the absorber that the particle crosses..

8. Nov 26, 2012

### Staff: Mentor

Maybe it is just the interpretation of the parameters:
If I0 corresponds to Pm (I think this should be P0) and I corresponds to Pi and a is positive:
Pi-Pm>0 (more pressure at i) corresponds to I<I0 (lower neutron flux at i).