tokens: have discussed the mechanisms that lead to the formation of instabilities in both the upstream and downstream medium when the magnetic field makes a large angle with the direction of the flow. We should note here that when we increase the angle even further beyond 70° this effect disappears since the component of the particle velocity parallel to the flow becomes smaller than the drift velocity if the thermal plasma, which eliminates the upstream current. The question remains as to why this result was not obtained with a hybrid code. By comparing our simulations with these earlier models we come to the conclusion that there are two factors that contribute to the different outcome. The number of particles . Although the absolute number of particles used in hybrid codes is far larger than what we use for the PI[MHD]C simulations, only a small fraction of the particles in hybrid simulations actually are suprathermal. Combined with the fact that for an oblique magnetic field only a fraction of the non-thermal particles are able to move upstream because of their pitch angle, we conclude that the hybrid simulations lacked the necessary number of particles to create the current that causes the disturbance of the upstream magnetic field. The size of the physical domain . The size of the simulated domain in the direction perpendicular to the shock-normal is six times larger in our model than in the original hybrid simulation. This allows us to capture the long wavelength that corrugates the shock and sets in motion the process that disturbs the upstream magnetic field. The smaller domain used by the hybrid simulation makes this impossible. We have tested our code with a physical domain similar to that used by Caprioli Spitkovsky ( 2014a ) and find that indeed the long wavelength never appears and so is the magnetic field amplification. These points demonstrate the opportunity that the PI[MHD]C method affords us. Because it is designed primarily to simulate large-scale structures, is less computationally expensive than PIC or hybrid methods and enables us to run the simulation in the frame of reference of the shock, it allows us to simulate a large volume of space, using a larger number of suprathermal particles, which in this particular case proved to be necessary. 2D3V PIC simulations of perpendicular and oblique shock configurations have been performed by Kato Takabe ( 2010 ) and Wieland et al. ( 2016 ), respectively. These studies verify that fast Alfvénic Mach (low magnetization) number shocks are mediated by the Weibel instability. These studies only report on electron thermalization but find pieces of evidence for the development of a proton non-thermal tail possibly connected with a shock surfing process in the perpendicular shock configuration. We confirm with Caprioli Spitkovsky ( 2014a ) that protons are accelerated at oblique shocks with an angle θ B = 45°. However, we argue that particle acceleration also proceeds at larger angles through
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