Owe to high-resolution observations made in both space-born and ground-based tele-scopes, solar small-scale activities (SSAs), such as Ellerman bombs (Ebs)and microflares (MFs), have recently become hot topics in solar physics. Because the relatively simple structures of SSAs are easy to study, but their physical mechanisms are more or less similar to major and complicated eruptions, such as major flares and coronal mass ejections, and so on, the study of SSAs will help to understand the physical nature of the major eruptions. Moreover, some studies also show that SSAs might contribute to some extent the heating of the solar atmosphere, which is still a puzzling problem in solar physics.In this paper we present a review on the study of SSAs which mainly appear in the solar lower atmosphere, the photosphere and chromosphere. We focus on Ebs and chromospheric MFs, although part of them could sometimes have emission in EUV, X-ray and radio wavebands. The study progress and the observational results of SSAs, including their configurations, sizes, lifetimes, spectra, velocities, magnetic fields, atmospheric models and the energy estimation etc., have been presented in details. The corresponding physical mechanisms and theoretical modellings have been described as well. In particular, magnetic reconnection in the solar lower atmosphere as a common and well-accepted mechanism for both Ebs and chromospheric MFs has been described. The difference of triggering mechanisms between Ebs and chromospheric MFs is that the reconnection occurs in the photosphere for the former, while in the chromosphere for the later.The direction of the future study has been discussed. We point out that the joint high-resolution observations in different wavebands are essentially important for understanding the physics and mechanism of SSAs. The theoretical modeling and numerical simulation should be compared with observations in details. Why and how a lower resistivity, which is necessary for the triggering of magnetic reconnection, could exist in the solar lower atmosphere is another important problem for understanding the magnetic reconnection.%随着观测的时间分辨率和空间分辨率的提高,近年来已发现和仔细研究了很多小尺度的太阳活动现象.它们的物理过程同复杂激烈的爆发现象有许多共同之处,因而可以为研究有复杂结构的激烈爆发现象(如耀斑和日冕物质抛射等)提供重要线索；同时,它们对太阳大气的加热可能有重要贡献,因而对理解太阳大气的加热机制有重要意义.太阳小尺度活动现象可以发生在太阳大气的不同高度,具有不同的物理特性.主要综述对太阳低层大气(光球和色球)中埃勒曼炸弹和微耀斑等小尺度活动现象的研究进展,包括它们的形态、大小、寿命、光谱、磁场和速度场、大气半经验模型和能量估计等,还介绍了已提出的各种模型和理论解释,特别是磁重联的模型.对今后的研究重点也进行了讨论.
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