Role of firehose instability in diffusive shock acceleration


Comparison of the contribution of pressure anisotropy to growth rates of instability with the contribution of current anisotropy of  distribution function of  the accelerated particles is carried out in shock prefronts of the supernova remnants. It is shown that the contribution of anisotropy of pressure can be important at disturbance scales close to gyroradii of the fastest accelerated particles.