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Solar Flare Activity and Variability of Electric Current Helicity

Chinese Journal of Astronomy and Astrophysics 2002年第1期2卷 81-91页

作者： KimJikSu Hong－QiZhang 等 pyongyangastronomicalobservatory AcademyofSciencesDPRofKorea NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012

Recent study using Huairou vector magnetograph data shows that durlug flare activity, the current helicity exhibits rapid and substantial variations and, in some cases, a recovering phase. We considered various representative the magnetic configurations. First, interacting twisted magnetic flux tubes are analyzed separately for positive, negative and mixed-sign helicity regions. The results show that the helicity during flares decreases in positive-sign, and increases in negative-sign regions. Then, flaring arcade also shows that the magnitude of the helicity decreases after flares. We also investigated current sheets formed by sheared magnetic field and showed that the current helicity (with either positive and negative signs) vanishes after reconnection. The emergence of twisted flux tubes which can trigger flares may be another source of flare-associated variability of current helicity. We demonstrate the relevance of current helicity to the description of flare activity by comparing its variation with that of shear angle in the active region AR 6891.

关键词： Sun: flare -Sun: current helicity - Sun: magnetic shear

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A Correlation between Proton Events and Hα Flares and its Possible Interpretation

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Chinese Journal of Astronomy and Astrophysics 2001年第6期1卷 537-548页

作者： KimJikSu Yuan-YongDeng KimKumSok KimJinSong NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 pyongyangastronomicalobservatory AcademyofSciencesDPRofKorea

Comparing space proton event data obtained during 1970-1980 with their identified Hα flare signatures we discover a peculiar correlation between them, according to which weak and small Ha flares can also produce proton events, and we reveal a characteristic 'triangle' distribution of Ha flares accompanying proton events. In order to explain such feature of proton events, we accept the acceleration mechanism by DC electric field. To deduce the parallel electric field we use the electric current helicity (or force-free parameter α) determined by the Huairou vector magnetograph. A comparison of E with E shows that the former is negligible in flaring sites. We show that in the flaring current sheet ion-anisotropy is generated, and it, in turn, gives rise to ion-anisotropic instability which competes with electric acceleration to give one possibility: the acceleration by DC electric field or annihilation of the built-up energy. The competition of DC acceleration and ionanisotropic instability annihilation in the current sheet gives a possible explanation for the above-mentioned 'triangle' character of the distribution.

关键词： Sun: flares - Sun: particle emission

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