对于耀斑热和非热本质的观测证认，涉及对耀斑的粒子加速、能量传输、耀斑区 能态学等一系列有关耀斑理论的重大问题的认识。Yohkoh卫星的发射和取得的观测研 究成果，使得对这些问题的认识大大提高了一步。Yohkoh卫星的观测得到了有关耀斑 脉冲相的热和非热现象的重要研究结果：(1) 证实了耀斑脉冲相双(足)源结构是较高能段 ($\geq 30$keV )硬X射线(HXR)发射的一般特征，且脉冲相双足源的非热特征也基本得 到证实 。(2) 发现了耀斑“环顶脉冲源”。该源的发现揭示了初始能量释放(可能是磁 重连)发生在软X射线耀斑环之上。这里可能正是从HXR源之上的重连点处朝下喷出的 等离子体流与下面的封闭磁环碰撞的位置；这首次显示了高能电子获取能量的位置。但 关于脉冲环顶源是热的或是非热的性质仍未从观测中得到肯定的结论。对耀斑的诊 断，高能粒子的传播，以及对非热电子谱的低能截止等问题进行了讨论。
Observed identification on thermal and non-thermal natures of solar flares is concerned in the knowledge of the important questions on flare theory, such as acceleration of particles in flares, energy transmission, and energetics of flare region. The successful launch of spacecraft Yohkoh, its observation, and relative research yields as well, greatly raise our knowledge of these questions forwards. The important results that have been made about thermal and non-thermal phenomena in impulsive flaring phase contain : (1) It is identified that the typical feature of HXR emission at higher energy bands (> 30keV) is the double (foot) sources occurred in the impulsive phase of flares. And the non-thermal nature of the double sources in impulsive phase is basically demonstrated. (2) The ``impulsive loop-top source'' of HXR emission in flares is discovered. The discovery of the source reveals that the primary energy release (probably magnetic reconnection) occurred above the apex of SXR loop. There is possibly the location that the plasma down- flowing from the reconnected site, which is somewhere above the SXR flaring loop-top, impinges upon the closed magnetic loop-top. It is the first time to show the position where the energetic particles are energized. However, it has not been answered properly that whether the impulsive HXR loop-top source is thermal or non-thermal in nature. The problems on diagnostic to flare models, energetic particles propagation, and the low energy cut-off of the non-thermal electrons are discussed.
Key words sun: X-ray---solar flare---radiation
mechanisms: thermal---radiation mechanisms: non-thermal