We examine the solar cycle distribution of major geomagnetic storms (Dst ≤ -100 nT), including intense storms at the level of -200 nT〈 Dst ≤ -100 nT, great storms at -300 nT〈 Dst ≤-200 nT, and super storms at Dst ≤ -300 nT, which occurred during the period of 1957-2006, based on Dst indices and smoothed monthly sunspot numbers. Statistics show that the majority (82%) of the geomagnetic storms at the level of Dst≤ -100 nT that occurred in the study pe- riod were intense geomagnetic storms, with 12.4% ranked as great storms and 5.6% as super storms. It is interesting to note that about 27% of the geomagnetic storms that occurred at all three intensity levels appeared in the ascending phase of a solar cycle, and about 73% in the descending one. Statistics also show that 76.9% of the intense storms, 79.6% of the great storms and 90.9% of the super storms occurred during the two years before a solar cycle reached its peak, or in the three years after it. The correlation between the size of a solar cycle and the percentage of major storms that occurred, during the period from two years prior to maximum to three years af- ter it, is investigated. Finally, the properties of the multi-peak distribution for major geomagnetic storms in each solar cycle is investigated.
Gui-Ming LeZi-Yu CaiHua-Ning WangZhi-Qiang YinPeng Li
[1]The 15-month climatology of medium-scale traveling ionospheric disturbances (MSTIDs) during a solar minimum...
Feng Ding,Weixing Wan,Guirong Xu,Tao Yu,Guanglin Yang, and Jing-song Wang 1 Beijing National Observatory of Space Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,China. 2 Institute of Heavy Rain,China Meteorological Administration, Wuhan,China. 3National Center for Space Weather,China Meteorological Administration,Beijing,China.
A range of analysis approaches,namely continuous wavelet,cross wavelet,and wavelet coherence analyses,are employed to clarify the phase relationship between the smoothed monthly mean sunspot number and solar 10.7 cm flux(F10.7).Analysis shows that there is a region of high spectral power sitting across the Schwabe cycle belt,where the two time series are in phase.However,analysis of the cross-wavelet transform and wavelet coherence unveils asynchronous behavior featured with phase mixing in the high-frequency components of sunspot activity and solar F10.7,which may explain the different activity properties of the photosphere and corona on a short time scale.
This is a study designed to analyze the relationship between ground level enhancements(GLEs)and their associated solar active regions during solar cycles 22and 23.Results show that 90.3%of the GLE events that are investigated are accompanied by X-class flares,and that 77.4%of the GLE events originate from super active regions.It is found that the intensity of a GLE event is strongly associated with the specific position of an active region where the GLE event occurs.As a consequence,the GLE events having a peak increase rate exceeding 50%occur in a longitudinal range from W20 to W100.Moreover,the largest GLE events occur in a heliographic longitude at roughly W60.Additionally,an analysis is made to understand the distributional pattern of the Carrington longitude of the active regions that have generated the GLE events.
日冕物质抛射(Coronal Mass Ejection,简称CME)可在短时间内将约1011~1013千克物质抛向行星际空间,是灾害性空间天气的主要驱动源之一.CME引发的空间天气事件可能会对卫星、航空器、航天器、电网、输油管道,以及航天员、航班机组人员和乘客健康造成严重危害.CME源区研究是理解CME的重要途径.本文旨在介绍近年来CME源区观测和理论研究进展,通过综合Hinode、STEREO、SDO等卫星的最新观测结果,对CME源区的观测特征进行描述;在此基础上,对stealth CME、twin-CME、大尺度活动等概念、观测现象背后的磁场机制、磁绳的观测和模拟,新的日冕磁场外推方法、CME的三维重构等进行概述.CME预报仍是目前空间天气领域的难点之一,结合最新观测数据对CME事件及其源区、尤其是源区大尺度磁场结构进行分析,对理解和预报CME及相关的空间天气事件具有重要意义.