Magnetic reconnection is considered to be the fundamental process by which magnetic energy is converted into plasma or particle kinetic energy.Magnetic reconnection is a widely applied physics model to explain the solar eruption events,such as coronal bright points(CBPs).Meanwhile,it is an usual way of the solar physics research to look for the observational evidences of magnetic reconnection in the solar eruption events in order to support the model.In this paper,we have explored the evidences of magnetic reconnection in a CBP observed by the Atmospheric Imaging Assembly(AIA)onboard the Solar Dynamics Observatory(SDO)at NOAA No.11163 on 2011 March 5.Our observations show that this event is a small-scale loop system in active regions that have similar size as a traditional CBP and it might shed light on the physics of a traditional CBP.This CBP is bright in all nine AIA wavelengths and displays a flaring development with three bursts intermittently.Each burst exhibits a pair of bi-directional jets almost along a line.They originate from the same position(CBP core),then move in the opposite directions.Our findings are well consistent with the magnetic reconnection process by which the bi-directional plasma outflows are produced and radiate the bi-directional jets detected by SDO/AIA.These facts further support the conclusion that the CBP is produced by the magnetic reconnection process.
With the aim of studying the relationship between the relative motions of the loop-top （LT） source and footpoints （FPs） during the rising phase of solar flares, we give a detailed analysis of the X7.1 class flare that occurred on 2005 January 20. The flare was clearly observed by RHESSI, showing a distinct X-ray flaring loop with a bright LT source and two well-defined hard X-ray （HXR） FPs. In particular, we correct the projection effect for the positions of the FPs and magnetic polarity inversion line. We find that： （1） The LT source showed an obvious U-shaped trajectory. The source of the higher energy LT shows a faster downward/upward speed. （2） The evolution of FPs was temporally correlated with that of the LT source. The converging/separating motion of FPs corresponds to the downward/upward motion of the LT source. （3） The initial flare shear of this event is found to be nearly 50 degrees, and it has a fluctuating decrease throughout the contraction phase as well as the expansion phase. （4） Four peaks of the time profile of the unshearing rate are found to be temporally correlated with peaks in the HXR emission flux. This flare supports the overall contraction pic- ture of flares： a descending motion of the LT source, in addition to converging and unshearing motion of FPs. All results indicate that the magnetic field was very highly sheared before the onset of the flare.
Tuan-Hui ZhouJun-Feng WangDong LiQi-Wu SongVictor MelnikovHai-Sheng Ji
We carry out a detailed analysis of the X3.5 solar flare that occurred on 2002 July 20, which is the strongest partially limb-occulted flare ever observed by the RHESSI satellite. The main results are： （1） during the main impulsive phase that lasts ,-10 minutes, the motion of the thermal sources follows a U-shaped trajectory. Nonthermal sources move in a similar way, but in a series of larger zigzags. We further show that the non-thermal sources are actually leading the contraction motion. （2） During the main impulsive phase, X-ray sources at different energies continuously form a loop-like configuration, with the highest energy source （up to ,- 100 keV） and the lowest energy source （down to ,- 10 keV） being located at two ends. The entire loop-like configuration moves in a U-shaped trajectory, while keeping the order of descending energy from highest to lowest during motion. Two non-thermal hard X- ray sources with different energies are spatially well separated in the distribution. The unusual complexities of the X-ray emissions in the tenuous solar corona challenge interpretations using bremsstrahlung in a simple magnetic configuration.
Jin-Hua ShenVictor MelnikovTuan-Hui ZhouHai-Sheng Ji
"Solar storm" has been commonly accepted by academic community and the public as a very popular scientific term. It is avivid description of violent ejections of a huge amount of magnetized plasma from the Sun as strong flare/CMEs, which sweepover into interplanetary space, develop, and affect our space environment. The solar storm could bring us disastrous spaceweather, destroy crucial technology, and cause a large-scale blackout. It is one of the natural disasters faced by modern humanbeings. Here we first briefly summarize the observational features of solar storms and introduce some key issues, and then wefocus on major advances in observational studies. We mainly introduce the efforts made by the Chinese scientists and comment on the challenges and opportunities that they are facing. In this era when scientific breakthroughs in solar storm studiescrucially depend on space-borne devices and large-aperture ground-based telescopes, the Chinese solar research communityneeds to develop its own major observational facilities and improve space weather forecasting abilities.
