Analyzing the Variations in the Spectral Energy Distribution of the Flat Spectrum Radio Quasar 3C 279

The spectral energy distributions (SEDs) of 29 states of 3C 279 are collected as samples, and the steady-state broken power-law electron energy distribution (EED) is applied.Then the relationship between the external observation and the internal physical properties of the source light is studied. Our main results are as follows:(1) Our results support the shock wave interpretation of photovariation (but require oblique shock) or magnetic reconnection interpretation. (2) There is a significant inverse correlation between EC peak luminosity logν_EC^pkL_EC^pk and magnetic field logB. There is a positive correlation between Doppler factor logδ and EC peak luminosity logν_EC^pkL_EC^pk, which means that the increase of Doppler factor is one of the reasons for the increase of EC peak luminosity. (3) There is no significant positive correlation between the synchronous peak frequency logν_syn^pk and peak luminosity logν_syn^pkL_syn^pk, which means that the sequence of flares may not be valid for all flares. (4) The parameter U_e/U_B (the ratio of relativistic electron energy density to magnetic field energy density) is far from 1, indicating that the equipartition trend between relativistic electron and magnetic field is not obvious, and 86% of parameters U_e/U_B have a ratio greater than 1, which means that most of the jets in 3C 279 are dominated by particles. From the relation of P_B (magnetic field power)< P_r (radiation power)< P_e (relativistic electron power)< P_p (cold proton power), P_p/P_jet (ratio of cold proton power to jet power) > 0.5, it indicates that the energy in 3C 279 jet is also carried by cold protons. Meanwhile, we find that the gamma-ray dissipation region in 3C 279 is located at 0.1-1.8 PC from the black hole center, suggesting that they are located outside the broad-line region (BLR) and within the dusty Torus (DT).