# why cosmic ray intensity needs correction with pressure?

by sctheorist
Tags: correction, cosmic, intensity, pressure
 P: 4 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...
 Mentor P: 9,588 More context would help. A correction where, and depending on which pressure?
 P: 4 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...
Mentor
P: 14,636

## why cosmic ray intensity needs correction with pressure?

The higher the pressure, the more material (air) is above you and the fewer cosmic rays get through.
 P: 4 Look Vanadium 50, 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...
 Mentor P: 14,636 Look, sctheorist (why so rude?) the sign of the correction depends on the sign of a.
 P: 4 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..
Mentor
P: 9,588
Maybe it is just the interpretation of the parameters:
 Quote by 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...
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).

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