太阳耀斑爆发时,日冕中磁自由能通过磁重联在短时间内转换成其他形式的能量,并伴随等离子体的加速和加热,以及带电粒子的加速。在这些过程中,宏观电场的出现起到关键的作用。但是到目前为止,由于太阳上宏观电场的探测比较困难,对电场的研究较少。近几年来随着一系列空间探测卫星被投入使用,加深了人们对日地空间事件发生、发展的物理过程的认识。但是太阳爆发和日冕加热机制等磁活动现象没有得到本质上的认识。太阳宏观电场的探测对突破这一瓶颈具有重要作用。综述了国内外在太阳宏观电场测量上的进展,并提出中国巨型望远镜(ChineseGiant Solar Telescope)在宏观电场观测上可能的科学目标。
This research aims for an objective identification, tracking, and a statistical analysis of the Moving Magnetic Features (MMFs) around sunspots using SOHO/MDI high-resolution magnetograms. To this end, we develop a computerized tracking program and study the motion and magnetism of the outflows of MMFs around 26 sunspots. Our method locates 4-27 MMFs per hour, with higher counts for large sunspots. We differentiate MMFs into type α that have a polarity opposite to the parent sunspots, and type β that share the sunspot's polarity. These sunspots' MMF subsets exhibit a wide range of central tendencies which have distinctive correlations with the sunspots. In general, α-MMFs emerge farther from the sunspot, carry less flux, and move faster than β-MMFs. The typical α/β-MMFs emerge at 2.2 - 8.1/0.1 - 3.2 Mm outside the penumbra limb, with lifetimes of 1.1 - 3.1/1.3 - 2.0 h. They are 1.1 - 6.6/1.4 - 3.6 Mm2 in area and carry 1.4 - 12.5/4.8 - 11.4 ×1018 Mx of flux. They travel a distance of 2.7 - 5.9/2.8 - 3.6 Mm with the speed of 0.5 - 0.9/0.4 - 0.7 km/s. Compared to the α-MMFs produced by large sunspots, those of small spots are smaller. They emerge closer to sunspot, move farther, live longer, and carry less flux. β-MMFs show much less correlation with the sunspots. The flux outflow carried by the MMFs ranges from 0.2 to 8.3 × 1019Mx· h-1 and does not show obvious correlation with the sunspots' evolution. The frequency distributions of the MMFs' distance traveled, area, and flux are exponential. This suggests the existence of numerous small, weak, and short-timescale magnetic objects which might contribute to the sunspot flux outflow.
This paper summarizes current helicity measurements in the solar active regions (ARs). There is a basic agreement with the "hemispheric sign rule (HSR)" of the current helicity among different vector magnetographs through two solar cycles, but there is a large dispersion of the fraction of ARs following the HSR. In our sample, there are 50%-78% ARs in solar cycle 22 and 44%-79% ARs in cycle 23 following the HSR. A variation is also found in the fraction of the ARs following the HSR between different instruments even when the same ARs are selected. The difference also exists for the same instrument when the selected ARs are different. There are some differences in the variation of HSR with solar cycle for the individual helicity parameter inferred from different instruments. Factors which influence the correlation of different data sets are analyzed.
In this paper, we study the correlation between the expansion speed of two-ribbon flares and the magnetic field measured in the ribbon location, and compare such correlation for two events with different magnetic configurations. These two events are: an M1.0 flare in the quiet sun on September 12, 2000 and an X2.3 flare in Active Region NOAA 9415 on April 10, 2001. The magnetic configuration of the M1.0 flare is simple, while that of X2.3 event is complex. We have derived a power-law correlation between the ribbon expansion speed (V r) and the longitudinal magnetic field (Bz) with an empirical relationship V r = A×Bz-δ, where A is a constant and δ is the index of the power-law correlation. We have found that δ for the M1.0 flare in the simple magnetic configuration is larger than that for the X2.3 flare in the complex magnetic configuration.
