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SUMMARY:Cosmic rays – origin\, composition\, interactions and applicatio
 ns
DTSTART;VALUE=DATE-TIME:20260521T073000Z
DTEND;VALUE=DATE-TIME:20260521T080000Z
DTSTAMP;VALUE=DATE-TIME:20260624T101552Z
UID:indico-contribution-3816@indico.tlabs.ac.za
DESCRIPTION:Speakers: Nadir Hashim (Kenyatta University)\nThis presentatio
 n highlights the origin of cosmic radiation\, their interactions in the ea
 rth’s atmosphere\, their measurements and their applications. The work b
 y Theodore Wulf and Victor Hess showed increased rates ionization with hei
 ght above the ground. This observation led to the conclusion that the sour
 ce of ionization is not from the earth but from space. That marked the dis
 covery of cosmic radiation. Over the years\, there has been extensive rese
 arch work carried out in order to understand cosmic radiation. It is now k
 nown that the primary cosmic ray particles comprise of about 85% protons\,
  12% helium\, 3% iron and other heavier elements. These primary cosmic ray
  particles interact with nuclei in the earth’s atmosphere to produce sec
 ondary particles such as kaons\, pions\, neutrons. The kaons and pions dec
 ay into muons which further decay into electrons. Neutrinos are produced i
 n these decay processes. Experimental data shows that the all-particle cos
 mic ray energy spectrum follows a simple power law with a spectral index o
 f about 2.7. However\, the value of the spectral index changes at cosmic r
 ay energies of about 10^6 GeV – known as the “knee” region and 10^9 
 GeV known as the “ankle” region. The bending of the spectrum at the kn
 ee region is attributed to the varied energy loses due to the difference i
 n masses of the cosmic ray particles at those energies. Cosmic ray particl
 es with energies beyond 10^9 GeV have been observed by several experiments
 . These are known as Ultra-High-Energy-Cosmic-Ray (UHECR) particles. The U
 HECR particles are thought to be of extra-galactic origin. These particles
  lose a large fraction of their energies when they interact with photons f
 rom the Cosmic Microwave Background Radiation (CMBR). This leads to a dras
 tic cut-off on the cosmic ray energy spectrum – known as the Greisen-Zat
 sepin-Kuzmin (GZK) cut-off. The earth’s magnetic field acts as a shield 
 for charged cosmic ray particles. Exposure to cosmic radiation is therefor
 e not only dependent on the altitude but also on the latitude on the earth
  surface. The dose due to cosmic radiation is minimum around the equator a
 nd increases as one moves away from the equator. On the earth surface\, co
 smic radiation comprises mostly of cosmic ray muons. These cosmic ray muon
 s are useful in imaging large structures like volcanos and pyramids on the
  earth. They are also useful in security applications and in the nuclear i
 ndustry. In the field of agricultural science\, the flux of cosmic ray neu
 trons on the earth surface provides a reliable and efficient means of moni
 toring the moisture content of the soil. The knowledge of cosmic radiation
  in our earth’s atmosphere and on the earth has applications in diverse 
 fields of science and technology in support of our development goals at th
 e national\, regional and global levels.\n\nhttps://indico.tlabs.ac.za/eve
 nt/139/contributions/3816/
LOCATION:NRF-iThemba LABS\, Old Faure Road\, Cape Town Auditorium
URL:https://indico.tlabs.ac.za/event/139/contributions/3816/
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