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Supernova remnants and γ - ray sources
 The particle acceleration mechanism «diffusive shock acceleration,
 which naturally leads to a power-law(幂指数) population of relativistic particles.
 In the version particles are scattered by magnetohydrodynamic waves repeatedly through the shock front. Electrons suffer synchrotron losses, producing the non-thermal emission from radio to X-rays usually seen in shell-type SNRs.
 The maximum energy depend on shock speed and age.
 Phenomenological model for the hadronic g-ray emission in SNRs and their environs.
 Relativistic Bremsstrahlung
 Diffusion of CRs and g-ray spectral evolution
 sample and correlation
 SNRs coincident with g–ray sources
 pulsars within the EGRET error boxes
 variability
The energy decreases:
a ratio:
 t2 is the actual age of the SNR
 we shall assume the initial time t1 as that obtained when the SNR has swept about 5 Mq of interstellar material, starting then the Sedov phase .???
(the typical t1 is 200-2000 years)
 ECR1=ECR2» ECR3 » 3qESN/4pR3
 he hadronic g-ray flux is;
 the flux provided by the previous equation is far too low to produce a detectable EGRET source.
 The expected g-ray flux in the Tev region by SNRs
 To extrapolate the GeV flux up to TeV energies we assume
 the flux in any given energy interval E1–E2 is just,
 In any case, this extrapolation will always provide an upper bound to the high-energy photon flux.
 The g-ray emissivity at a given energy E from relativistic Bremsstrahlung is
 We are interested in the g-ray radiation above 100 MeV,
 This same population of relativistic electrons will also radiate at radio wavelengths, via the synchrotron mechanism. The synchrotron spectrum of a power-law electron energy distribution is
 the ratio between the g-ray flux emitted by relativistic Bremsstrahlung and the synchrotron emission results
3 Diffusion of CRs and g-ray spectral evolution
 The spectrum of g-rays generated through p0-decay at a source of proton density np is
 If the proton spectrum Jp(Ep) at the g-ray production site is:
 We also expected a power-law spectrum at g-ray
 If there is diffusion, we shall have, instead
[f (Ep,r,t)is the distribution function of protons]
 f satisfies the well-known diffusion equation
 But we obserbved(different from the expected particle population )
 Summing up, special care must be taken in analyzing the a priori expectations for the SNR-cloudy medium scenario.
(the distanse to the cloud and the diffusion index)