标题： 耀斑期间的硬X射线辐射与光球磁场变化 显示英文标题

标题： Hard X-ray Emission During Flares and Photospheric Field Changes

摘要： 我们研究了由GONG和HMI仪器观测到的X级耀斑期间磁场突然永久变化与RHESSI观测到的硬X射线（HXR）辐射之间的相关性，以关联光球磁场的变化与日冕重构，并探讨磁场变化的起源。我们发现，在空间上，早期的RHESSI辐射很好地对应于强磁场变化的位置。这些磁场变化主要发生在极向反转线（PIL）附近的强磁场区域。随着耀斑足点远离PIL，后期的RHESSI辐射并不对应显著的磁场变化。大多数磁场变化开始于可检测到的HXR信号之前或同时，且它们结束的时间与可检测到的HXR耀斑辐射相同或稍晚。在耀斑的后期阶段，一些磁场变化以接近HXR足点速度的速度传播。磁场变化的传播通常发生在HXR信号最强峰值之后，当足点开始远离PIL时，即磁场变化沿着与HXR足点相同的轨迹移动，但时间更早。因此，磁场变化和HXR辐射在时空上相关，但并非共空间或同时发生。我们还发现，在最强的X级耀斑中，磁场变化的幅度峰值比HXR信号的峰值提前几分钟。我们简要讨论了这种观测到的时间延迟与爆发期间电流片形成的关系。 显示英文摘要

摘要： We study the correlation between abrupt permanent changes of magnetic field during X-class flares observed by the GONG and HMI instruments, and the hard X-ray (HXR) emission observed by RHESSI, to relate the photospheric field changes to the coronal restructuring and investigate the origin of the field changes. We find that spatially the early RHESSI emission corresponds well to locations of the strong field changes. The field changes occur predominantly in the regions of strong magnetic field near the polarity inversion line (PIL). The later RHESSI emission does not correspond to significant field changes as the flare footpoints are moving away from the PIL. Most of the field changes start before or around the start time of the detectable HXR signal, and they end at about the same time or later than the detectable HXR flare emission. Some of the field changes propagate with speed close to that of the HXR footpoint at a later phase of the flare. The propagation of the field changes often takes place after the strongest peak in the HXR signal when the footpoints start moving away from the PIL, i.e. the field changes follow the same trajectory as the HXR footpoint, but at an earlier time. Thus, the field changes and HXR emission are spatio-temporally related but not co-spatial nor simultaneous. We also find that in the strongest X-class flares the amplitudes of the field changes peak a few minutes earlier than the peak of the HXR signal. We briefly discuss this observed time delay in terms of the formation of current sheets during eruptions.