目前的第24個太陽週期相較於前一個第23甚至是第22個太陽週期都要弱，這暗示著一般而言應有較弱的太陽風造成地球磁層變大的情形，然而近幾年卻有很多中等強度的磁暴伴隨著非常不尋常的現象發生，如：地球同步軌道的磁層頂穿越與中緯度極光的現象。而在先前的太陽週期，這些現象是發生於非常強的磁暴情況，本週期這些不尋常的現象或許可用地球磁層變小來解釋。在本計畫我們將分析2011年至2017年間的13個磁暴事件，藉由比較磁層頂穿越資料、極冠大小與現有模型來證實該效應，其中的磁層頂穿越將由GOES及ERG衛星資料提供，極冠區域將使用觀測太陽高能粒子貫穿至極區的POES及Van-Allen衛星資料來決定。這項研究對於了解太陽風–磁層耦合的長期變化將能提供重要貢獻，亦將改善我們對於太空天氣的預報能力。 ;The current 24th solar cycle is weak in comparison with the previous 23rd and especially 22nd one. The low solar activity implies a relatively weak solar wind driving that should result in increasing of the magnetosphere size in general. However during recent years, a number of moderate magnetic storms were accompanied by very unusual phenomena such as magnetopause crossings of geosynchronous orbit and aurora borealis at middle latitudes. In the previous solar cycles, those effects occurred rather during severe and strong magnetic storms. The unusual dynamics might be explained by a decrease of the magnetosphere size during the 24th solar cycle. It is proposed to verify this effect by comparison of experimental data on the magnetopause crossings and the size of polar cap with predictions of existing models during 13 magnetic storms occurred from 2011 to 2017. The crossings will be identified with using geosynchronous and high-apogee satellites, such as GOES and ERG missions. The polar cap will be determined using POES and Van-Allen missions, which observe solar energetic particles penetrating to the polar region. The study will provide an important contribution to understanding of the long-term variations in the solar wind – magnetosphere coupling and will improve our capabilities in the space weather prediction.
