NAOC Open IR  > 太阳物理研究部
Analysis of a delta spot
Liu, Y; Zhang, HQ
Abstractdelta-groups generally develop in three different ways: eruption of a single complex active region, eruption of large satellite spots near a large older spot, or collision of spots of opposite polarity from different dipoles. In this paper, we present a rare observational result in which a delta-spot forms from rapid coalescence of two opposite magnetic features in a pre-existing delta-configuration. The white-light (WL) observations of this delta-spot in active region NOAA 9077 were performed by TRACE. The time-lapse movie of the co-aligned WL images shows that the whole active region was undergoing rapid disintegration and reconstruction on 11{17 July 2000. The preceding (p) and following (f) components of the delta-spot continue to grow in size, while the active region is in the decaying phase. Their proper motions are determined as a function of time using SOHO/MDI full-disk magnetograms. A major are (3B/X5.7) erupted in the active region on 14 July. Initially, a relative shearing motion is visible between the p and f spots on this day. About two hours before the major are, the shearing motion suddenly stops and the velocities change significantly. The ribbons of the are are located just outside of the delta-configuration. An interesting finding is the sign reversal of the helicity of the f spot also just 2 hours before the are. The delta-spot obviously separates after the are. Our results clearly demonstrate that helicity reversal in magnetic features of a delta-configuration is likely to destabilize the compact structure, as well as to re-organize the magnetic field configuration, and, hence, is important for the rapid disintegration of a delta-spot during major flares. A model is presented to explain why a spot can change its chirality.
KeywordSun : Magnetic Fields Sun : Sunspots Sun : Flares
Indexed BySCI
WOS IDWOS:000175132400024
Citation statistics
Cited Times:18[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
AffiliationChinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
Recommended Citation
GB/T 7714
Liu, Y,Zhang, HQ. Analysis of a delta spot[J]. ASTRONOMY & ASTROPHYSICS,2002,386(2):646-652.
APA Liu, Y,&Zhang, HQ.(2002).Analysis of a delta spot.ASTRONOMY & ASTROPHYSICS,386(2),646-652.
MLA Liu, Y,et al."Analysis of a delta spot".ASTRONOMY & ASTROPHYSICS 386.2(2002):646-652.
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