What does the Sun tell and hint now?
What does the Sun tell and hint now?作者机构：National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences
出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)
年 卷 期：2009年第9卷第9期
页 面：959-965页
核心收录：
学科分类：0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 070401[理学-天体物理] 0704[理学-天文学] 0825[工学-航空宇航科学与技术]
基 金：Supported by the National Natural Science Foundation of China(Grant Nos.10583032 and 40636031) the National Key Research Science Foundation(2006CB806303)
主 题：Sun: activity Sun: general sunspots
摘 要：Some historical records, which have held since the beginning of modern solar activity cycles, are being broken by the present Sun： cycle 23 records the longest cycle length and fall time; latitudes of high-latitude sunspots belonging to a new cycle around the minimum time of the cycle are statistically the lowest at present, compared with those of other cycles; there are only one or no sunspots in a month appearing at high latitudes for 58 months, which is the first time that such a long duration has been observed. The solar dynamo is believed to be slowing down due to： （1） the minimum smoothed monthly mean sunspot number is the smallest since cycle 16 onwards, and even probably among all modern solar cycles; and （2） once the time interval between the first observations of two neighboring sunspot groups is larger than 14 d, it should be approximately regarded as an observation of no sunspots on the visible solar disk, called a spotless event. Spotless events occur with the highest frequency around the minimum time of cycle 24, and the longest spotless event also appears around the minimum time for observations of the Sun since cycle 16. Cycle 24 is expected to have the lowest level of sunspot activity from cycle 16 onwards and even probably for all of the modern solar cycles.
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