Supernova remnants (SNRs) appear to be the only viable class of galactic source of cosmic rays up to the knee or even up to the ankle energy. The maximum attainable energy is one of the key unsettled issues concerning the SNR model of cosmic ray origin. In recent theoretical developments of the diffusive shock acceleration (DSA) in SNRs, protons are expected to accelerate at least up to the knee energy for the amplified magnetic fields. Under the SNR origin of cosmic ray framework, the mass composition of cosmic rays will be heavier than proton mass beyond the knee. The conclusions of different EAS experiments on primary mass composition in the PeV energy region are, however not unequivocal. The accurate determination of mass composition is expected to throw important light on the origin of the knee feature as well as the origin of cosmic rays. Under this context, the following points will be addressed in the presentation:
• The consequences of the maximum attainable energy of cosmic rays in SNR as the atomic number times the knee energy, achievable under amplified magnetic field scenarios. The secondary gamma-ray spectrum of young SNRs and the molecular clouds associated with the SNR will be presented.
• An alternative approach to evaluate the mass composition of primary cosmic rays above the knee of their energy spectrum through the study of high-energy gamma rays, muons, and neutrinos produced in the interactions of cosmic rays with solar ambient matter and radiation as a cosmic ray mass spectrometric technique will also be explored.
• Monte Carlo simulations suggest the existence of the knee in the primary cosmic ray energy spectrum. Different components of cosmic ray extensive air shower beyond the knee of the energy spectrum will be discussed.
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