Statistical Analysis on XMM-Newton X-Ray Flares of Mrk 421: Distributions of Peak Flux and Flaring Time Duration

The energy dissipation mechanism in blazar jet is unknown. Blazar flares could provide insights into this problem. Here we report statistical results of XMM-Newton observations of X-ray flares in Mrk 421. We analyze all public XMM-Newton X-ray observations for Mrk 421, and construct the light curves. Through fitting the light curves, we obtain the flare-profile parameters, such as peak flux (F-p) and flaring time duration (T-fl). It is found that the distributions of F-p and T-fl both obey a power-law form, with the same index of alpha(F) = alpha(T) approximate to 1. The statistical properties are consistent with the predictions for a self-organized criticality system with energy dissipation in one-dimensional space. This is similar to a solar flare, but with different space dimensions of the energy dissipation domain. This suggests that the X-ray flaers of Mrk 421 might be driven by a magnetic reconnection mechanism. Moreover, in the analysis, we find that variability on a timescale of similar to 1000 s appears frequently. This rapid variability indicates a magnetic field of >= 2.1 delta(-1/3)(D) G (delta(D) is the Doppler factor) in the emission region.