Signature of Stochastic Acceleration and Jet Energetics in the X-ray Spectrum of Mrk 421

We present the results of a deep spectral analysis of all Swift observations of Mrk 421 between April 2006 and July 2006, when it reached its highest X-ray flux recorded until the end of 2006. We investigate the correlation between the spectral parameters and we find signature of both stochastic acceleration and energetic budget of the jet.