The phenomenon of quasi-periodic pulsations (QPPs) in solar and stellar flares has been known for over 50 years and significant progress has been made in this research area. It has become clear that QPPs are not rare—they are found in many flares and, therefore, robust flare models should reproduce their properties in a natural way. At least fifteen mechanisms/models have been developed to explain QPPs in solar flares, which mainly assume the presence of magnetohydrodynamic (MHD) oscillations in coronal structures (magnetic loops and current sheets) or quasi-periodic regimes of magnetic reconnection. We review the most important and interesting results on flare QPPs, with an emphasis on the results of recent years, and we present the predicted and prominent observational signatures of each of the fifteen mechanisms. However, it is not yet possible to draw an unambiguous conclusion as to the correct underlying QPP mechanism because of the qualitative, rather than quantitative, nature of most of the models and also due to insufficient observational information on the physical properties of the flare region, in particular the spatial structure of the QPP source. We also review QPPs in stellar flares, where progress is largely based on solar-stellar analogies, suggesting similarities in the physical processes in flare regions on the Sun and magnetoactive stars. The presence of QPPs with similar properties in solar and stellar flares is, in itself, a strong additional argument in favor of the likelihood of solar-stellar analogies. Hence, advancing our understanding of QPPs in solar flares provides an important additional channel of information about stellar flares. However, further work in both theory/simulations and in observations is needed.

太阳耀斑和恒星耀斑中的准周期脉动 (QPP) 现象已经为人所知 50 多年，并且在该研究领域取得了重大进展。很明显，QPP 并不罕见——它们存在于许多耀斑中，因此，强大的耀斑模型应该以自然的方式再现它们的特性。已经开发了至少 15 种机制/模型来解释太阳耀斑中的 QPP，这些机制/模型主要假设日冕结构（磁环和电流片）或准周期性磁重联机制中存在磁流体动力学 (MHD) 振荡。我们回顾了耀斑 QPP 中最重要和最有趣的结果，重点是近年来的结果，并展示了 15 种机制中每一种的预测和显着观察特征。然而，由于大多数模型的性质而非定量性质，并且由于对耀斑区域物理特性的观测信息不足，特别是由于对耀斑区域物理特性的观测信息不足，因此尚不可能对正确的基础 QPP 机制得出明确的结论QPP 源的空间结构。我们还回顾了恒星耀斑中的 QPP，其中的进展主要基于太阳-恒星的类比，表明太阳耀斑区域和磁活性恒星的物理过程存在相似性。在太阳和恒星耀斑中存在具有相似特性的 QPP 本身就是一个强有力的额外论据，支持太阳-恒星类比的可能性。因此，提高我们对太阳耀斑中 QPP 的理解提供了一个重要的额外的恒星耀斑信息渠道。