Analyzing The Variations In The Spectral Energy Distribution Of The Blazar Mrk 421

Active galactic nuclei(AGN)refers to the central region of active galaxies,and the intense activity in this region attracts many astronomers to explore it.As a subclass of active galactic nuclei,the activity processes and structures in the radiation region can be understood by studying blazars.It also helps us understand more physical information in the radiation process.The first chapter of this thesis introduces the observation characteristic of AGN,the classification of AGN firstly,the unified model and the update of AGN model with the development of observation technology.The second chapter mainly introduces the observational characteristics of blazars,relativistic jet,energy spectrum distribution,the discussion of blazar sequences and variation of blazars.The third chapter mainly introduces the radiation mechanism of blazars and the leptonic model,the hadronic and lepto-hadronic models,and the spine?layer model.In chapter four,Synchronous Self-Compton model was used to fit the observation data of Mrk 421(z=0.031)in 31different time periods,and the fitting parameters of Mrk 421were obtained.Through calculating and analyzing the correlation between physical parameters we got the following results:(1)Our results support the shock wave interpretation of photovariation or magnetic reconnection interpretation.(2)A size relation>₀)>>shows that the jet process is dominated by particles.(3)The larger of the truncated Lorentz factor₍(7)of the electronic spectrum,the weaker the effect of radiation cooling.(4)The relationship betweenthe peak luminosity ratio of Mrk 421and the intensity of the magnetic field implies that when the magnetic field increases,the cooling effect of synchrotron radiation also increase during the cooling process of the entire jet.(5)The relationship between and the intensity of the magnetic field indicates that the change of the electron energy spectrum is closely related to the change of the magnetic field.The fifth chapter expands the sample,collects the observation data of Mrk 421 in 40 different time periods,Mrk 501 in 22 different time periods,and 3C 454.3 in 12 different time periods from the literature,carries on the model fitting,and analyzed.The results to show that the peak luminosity change of Mrk 501 may be related to electron energy spectrum and doppler factor?.The factors affecting the luminosity change of Mrk 421 still need to be further explored.