John A. Poirier

Professor Emeritus,
Astrophysics and Elementary Particle Physics

Research Interests

An astrophysicist studying cosmic rays, he operates an extensive air shower array utilizing position sensitive detectors. The properties of primary cosmic rays in the energy region 10 GeV to 300 GeV are studied using data of single track muon secondaries. The properties of primary cosmic rays above 100,000 GeV are studied using extensive air shower data of secondary electrons and muons.

Experiments with cosmic rays are conducted with 512 proportional wire chambers. The 100m x 100m array is located a block from campus. Ultra-high-energy cosmic rays with energies above 100 trillion electron volts (TeV), are explored. The array also studies the primary cosmic ray energy region 0.03 to 1.0 TeV utilizing muon tracks.

Gamma rays are undeflected as they travel through interstellar space and thus gamma shower angles pinpoint their origins. The energy of the primary can be obtained from the number of secondary shower particles.

The detector distinguishes each secondary track as muon or electron. Identified muon tracks of an extensive air shower can be extrapolated backward (upward) to find their apparent height of origin which is related to its cross-section in air. This data thus enables us to measure the atomic composition of cosmic rays from 100 TeV to 100,000 TeV. By comparing our counting rate of muon secondaries with solar flares and coronal mass ejections, we have established a six sigma coincidence thus showing the sun capable of accelerating protons to energies of >10 GeV.

“Distributions of secondary muons at sea level from cosmic gamma rays below 10 TeV,” J. Poirier, S. Roesler, and A. Fassò, Astroparticle Physics 17, 4, 441-458 (2002).

“Ground level muons in coincidence with the solar flare of April 15, 2001,” J. Poirier and C. D'Andrea, J. Geophys. Res., Space Physics, Vol. 107(A11) 1376-1384 (2002).

 
“Search for sub-TeV gamma rays in coincidence with gamma ray bursts,” J. Poirier, C. D'Andrea, P.C. Fragile, J. Gress, G.J. Mathews, and D. Race, Phys. Rev. D67, 042001, 1-6 (2003).

“Constraints on models for TeV gamma rays from gamma-ray bursts,” P.C. Fragile, G.J. Mathews, J. Poirier, T. Totani, Astroparticle Physics 20, 591-607 (2004).

“Ground level muons coincident with the 20 January 2005 solar flare,” C. D’Andrea and J. Poirier, Geophys. Res. Lett. 32, L14102 (2005).

Prof. Poirier has been an NSF postdoctoral fellow at CERN, Geneva, Switzerland.

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