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Динамика солнечной и геомагнитной активности. I. Источники геомагнитной активности, корональная масс-эжекция, высокоскоростные потоки солнечного ветра
The presented review ‘Solar and geomagnetic activity dynamics' contains the analysis of modern perceptions of relations between the geomagnetic activity and dynamic processes in the solar corona. The relations between the geomagnetic activity and solar processes were revealed in the mid-XIX century. The correlation of the number of solar bursts with the number of geomagnetic disturbances, as well as withthe number and brightness of aurorae was analyzed by Carrington in 1860, and 11-year periodicity in dynamics of the number of sunspots and dynamics of geomagnetic disturbances and aurorae was discovered. The geomagnetic activity is generated as a response of magnetosphere processes to the change of the structure of solar wind streams, i.e. it actually reflects the changes of the solar corona structure in the process of solar activity development. The most significant large-scale variations of geomagnetic activity (magnetic disturbances or storms) are related to the influence of coronal ejections and high-speed solar wind streams. Magnetic storms are effective drivers of a number of magnetosphere processes, the dynamics of which considerably determines the possibility of using the near-Earth space by the modern hi-tech society. The study of geomagnetic activity dynamics is closely related to the necessity of resolving a number of technical problems that arise during the operation of industrial power supply systems, satellites and communication systems (GPS-navigation, shortwave communication).The first part of review ‘Geomagnetic activity sources, coronal mass ejection (CME), high-speed solar wind streams (HSS)' deals with the basic issues related to the impact of changes in the structure of solar wind streams under the influence of CME and HSS on geomagnetic activity. Particularly, the specific differences of dynamics of solar wind parameters in the CME and HSS structures are demonstrated. In the process of solar activity development, the annual distribution of the number of CME and HSS (main sources of magnetic storms) changes, and, respectively, the contribution of each structure to the annual distribution of the number of geomagnetic storms and to the geomagnetic activity also changes. Dynamics of geomagnetic activity under the influence of CME and HSS (dynamics of CME- and HSS-storms) is related to formation of a number of structures that arise in the solar wind during the motion of coronal ejections and high-speed streams in the interplanetary space. The area of interaction of a coronal ejection and surrounding solar wind expands in the interplanetary space and reaches~0,2 - 0,3 АЕ near the Earth. This area of perturbed solar wind is called Interplanetary Coronal Mass Ejection (ICME). In front of the ICME area, a number of perturbed solar wind structures arise: fast shock wave, a hot dense plasma sheath is formed between the shock wave and leading edge of the coronal ejection. One of the CME types is represented by magnetic clouds (MC). During the expansion of HSS, an area of interaction between the low-speed and high-speed solar wind streams (Corotating Interaction Region (CIR)) is formed in the solar wind. The gradual increase of the solar wind speed is accompanied by the plasma temperature and density rising, as well as increase of magnetic field; the maximum values of these parameters are generally recorded up to the speed maximum. The main drivers of geomagnetic activity dynamics are the structures of the solar wind streams, which have been formed near the Earth during the expansion of CME and HSS: these are shock, plasma sheath, ejecta for CME storms and CIR, and HSS for HSS storms. In the growth phase and at the maximum of solar activity, the main sources of moderate geomagnetic storms (>50%) are the structures formed at CME (ICME + shock); in the decay phase and at the minimum of solar activity, the main sources of moderate geomagnetic storms are the structures formed und er the influence of HSS (CIR + HSS). The presence of a negative Bz component of the interplanetary magnetic field (IMF) in the structures of the solar wind streams increases the probability of formation of a magnetic storm and augmentation of its power. The review uses the experimental data on dynamics of parameters of the solar wind and interplanetary magnetic field in the ICME and CIR structures.