A Statistical Analysis of X1- and X2- or Higher-Class Flares during Solar Cycles 21∼23 |
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| Authors: | YANG Xing-xing LE Gui-ming ZHANG Cheng-yi YIN Zhi-qiang ZHAO Wei |
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| Institution: | 1. Nanjing University of Information Science and Technology, Nanjing 210044;2. National Center for Space Weather, Beijing 100081;3. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 |
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| Abstract: | The X1- and X2- or higher class ?ares in solar cycles 21, 22, and 23 from 1986 to 2008 have been analyzed statistically in this paper. It is found in the statistical study that the number of the X1-class ?ares accounted for 52.71% of total X- and higher class ?ares, while, the number of the X2- and higher class ?ares accounted for 47.29% of total X- and higher class ?ares. No matter whether the X1- and X2- or higher class ?ares, most of them occured in the descending phases of the solar cycles. Moreover, the weaker the intensity of the solar cycle, the higher the ratio of the ?ares occurred in the descending phase of the solar cycle, and the stronger the intensity of solar ?ares, the higher the ratio of the ?ares occurred in the descending phases of the solar cycles. In addition, the phase difference between the peak of the smoothed monthly mean number of sunspots and that of the X-class ?ares has been calculated, which shows that the smoothed monthly mean number of the X1-class ?ares had a very noticeable time advance of 1 month with respect to that of sunspots in the cycles 21 and 22, but there was a time lag of 13 months in the cycle 23, while, for the X2- and higher class ?ares, there was a time lag of 9 months in the cycle 21, but a one-month time advance existed in the cycle 22, and again a time lag of 32 months appeared in the cycle 23. |
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| Keywords: | sun flares&mdash sun sunspots&mdash sun activity |
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