Typical X-ray spectra of SNRs show either synchrotron emission from high energy electrons, thermal emission from shock-heated interstellar medium (ISM), or combination of these. The surrounding environment should be one of the key parameters (Patnaude et al. However it is still unclear what determines the efficiency. The diffusive shock acceleration mechanism (e.g., Malkov & Drury 2001) is believed to be the relevant mechanism, which can explain the power-law energy distribution. X-ray and GeV/TeV γ-ray observations have revealed that the shocks of supernova remnants (SNRs) are the acceleration sites of the Galactic cosmic rays up to the TeV range (e.g., Koyama et al. This result implies that the maximum energy of accelerated electrons in RCW 86 is higher in the low-density and higher shock speed regions.Ĭosmic rays are particles which bombard the Earth from anywhere (Hess 1912). It is discovered that the photon index of the nonthermal component becomes smaller when decreasing the emission measure of the shocked ISM, where the shock speed has remained high. The spacially resolved spectra are well reproduced with a combination of a power-law for synchrotron emission and a two-component optically thin thermal plasma, corresponding to the shocked interstellar medium (ISM) with kT of 0.3–0.6 keV and Fe-dominated ejecta. In this paper, we present results of spatially resolved spectroscopy of the entire remnant with Suzaku. Thus, the remnant provides a suitable laboratory to test possible association between the acceleration efficiency and the environment. These emission originate from the shock-heated plasma and accelerated electrons respectively, and their intensities reflect their density distributions. The SNR RCW 86 shows both thermal and nonthermal X-ray emission with different spatial morphologies. The surrounding environment could be one of the key parameters. However, it is unknown what determines the maximum energy of accelerated particles. Diffusive shock acceleration by the shockwaves in supernova remnants (SNRs) is widely accepted as the dominant source for Galactic cosmic rays.