The jets of blazars are renowned for their multi-wavelength flares and rapid extreme variability; however, there are still some important unanswered questions about the physical processes responsible for these spectral and temporal changes in emission properties. In this paper, we develop a time-dependent particle evolution model for the time-varying emission spectrum of blazars. In the model, we introduce time-dependent electric and magnetic fields, which consistently include the variability of relevant physical quantities in the transport equation. The evolution on the electron distribution is numerically solved from a generalized transport equation that contains the terms describing the electrostatic, first-order and second-order \emph{Fermi} acceleration, escape of particles due to both advection and spatial diffusion, as well as energy losses due to the synchrotron emission and inverse-Compton scattering of both synchrotron and external ambient photon fields. We find that the light curve profiles of blazars are consistent with the particle spectral evolution resulting from time-dependent electric and magnetic fields, rather than the effects of the acceleration or the cooling processes. The proposed model is able to simultaneously account for the variability of both the energy spectrum and the light curve profile of the BL Lac object Mrk 421 with reasonable assumptions about the physical parameters. The results strongly indicate that the magnetic field evolution in the dissipated region of a blazar jet can account for the variabilities.

中文翻译：

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与时间相关的粒子加速和发射模型：了解粒子光谱演化和耀斑耀斑

耀变体喷流以其多波长耀斑和快速的极端变化而闻名。然而，关于造成这些发射特性的光谱和时间变化的物理过程，仍有一些重要的未解决的问题。在本文中，我们为耀变体随时间变化的发射光谱开发了一个与时间相关的粒子演化模型。在模型中，我们引入了与时间相关的电场和磁场，它们始终包括输运方程中相关物理量的可变性。电子分布的演化是从广义传输方程数值求解的，该方程包含描述静电、一阶和二阶 \emph {Fermi} 加速度、由于平流和空间扩散导致的粒子逃逸的术语，以及由于同步加速器和外部环境光子场的同步加速器发射和逆康普顿散射引起的能量损失。我们发现耀变体的光变曲线与由时间相关的电场和磁场引起的粒子光谱演化一致，而不是加速或冷却过程的影响。所提出的模型能够同时解释 BL Lac 物体 Mrk 421 的能谱和光变曲线轮廓的可变性，同时对物理参数做出合理假设。结果强烈表明，耀变体喷流耗散区域的磁场演变可以解释这些变化。我们发现耀变体的光变曲线与由时间相关的电场和磁场引起的粒子光谱演化一致，而不是加速或冷却过程的影响。所提出的模型能够同时解释 BL Lac 物体 Mrk 421 的能谱和光变曲线轮廓的可变性，同时对物理参数做出合理假设。结果强烈表明，耀变体喷流耗散区域的磁场演变可以解释这些变化。我们发现耀变体的光变曲线与由时间相关的电场和磁场引起的粒子光谱演化一致，而不是加速或冷却过程的影响。所提出的模型能够同时解释 BL Lac 物体 Mrk 421 的能谱和光变曲线轮廓的可变性，同时对物理参数做出合理假设。结果强烈表明，耀变体喷流耗散区域的磁场演变可以解释这些变化。所提出的模型能够同时解释 BL Lac 物体 Mrk 421 的能谱和光变曲线轮廓的可变性，同时对物理参数做出合理假设。结果强烈表明，耀变体喷流耗散区域的磁场演变可以解释这些变化。所提出的模型能够同时解释 BL Lac 物体 Mrk 421 的能谱和光变曲线轮廓的可变性，同时对物理参数做出合理假设。结果强烈表明，耀变体喷流耗散区域的磁场演变可以解释这些变化。