I was trying to gather data to produce my own cosmic ray (CR) spectrum plot. I have relied on this very useful French database collecting past space-based CR measurements. If I try to insert the keyword "AllParticleFlux" in the Flux or ratio selection tab, I have 0 entries though.

Also looking in several plots of the literature CR spectra gathered by space-borne instruments, they are always sub-divided in the different elements they measure enter image description here (figure from https://arxiv.org/abs/1711.11432).

So I was wondering, what are the main difficulties (if there are) in making an "all-particle" spectrum from space-borne CR experiments?

My sense is that it is related to the fact that the energy in space are measured (usually) combining a magnetic spectrometer and a calorimeter measurement. The range of velocities measurables (i.e. the range of deflections in the spectrometer measurable) varies with the charge of the particle (simple Larmor radius formula). Same for the calorimeter, different response for different particles.
One would not obtain events in the same energy bins for different species and this would complicate summing-up the excesses.

What do you think is the reason? Does anyone have a reference for an "all-particle" CR spectrum measured in space?

  • $\begingroup$ Isn't "all particle" in this case just the netting of all of the particles observed? What you write seems to indicate that it means something else... $\endgroup$ – Kyle Kanos May 16 at 11:29
  • $\begingroup$ Yes the "all-particle" is just the total Cosmic Rays events observed. But the thing is that neither in the literature, nor in the database i linked, I could find an "all-particle" spectrum for the space-borne instruments. Maybe it is just my ignorance but I think they do not produce them. And I am not sure you can simply sum all the events from different species in the same energy bin. The main difference is that space-borne instrument can "tag" species while a ground-based cannot. $\endgroup$ – cosimoNigro May 16 at 11:41
  • $\begingroup$ For example the author of the paper I posted was trying to produce a global spline fit of the CR spectrum, I guess he would have used the "all-particle" measurements (black & white points) at low energies (i.e. from space) if there were any. $\endgroup$ – cosimoNigro May 16 at 11:45
  • $\begingroup$ Have you tried summing the individual fluxes up and seeing if it matches the "all particle" flux? $\endgroup$ – Kyle Kanos May 16 at 11:48
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    $\begingroup$ From a scientific perspective, having the per-nucleon breakdown is better, probably for a variety of reasons including studying the elemental composition of CRs. You can then net the nucelon fluxes manually to get the all particle, if needed. $\endgroup$ – Kyle Kanos May 16 at 12:03

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