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论文范文
1. Introduction The study of complexes of solar activity has quite a long history. It began, most likely, with the work by Gnevyshev [1], who proved that besides the 11-year cycles of solar activity there were shorter periods when the level of activity increased. He called them “pulses of activity.”These results were presented later by Eigenson et al. [2]. The following step was associated with Mt. Wilson magnetographic measurements covering the entire surface of the Sun. It was then that a more adequate term, “complexes of solar activity,” was proposed in [3–5] to characterize long-term (from months to years) enhancements of solar activity in a certain range of heliolongitudes. These authors actually claimed that the complexes of activity must comprise not only AR, but also unipolar magnetic regions and, hence, CH, which suggested their global nature. In [6], Obridko and Shelting introduced the notion of a “global complex of activity,” combining both local and global field structures. The study of such a complex feature requires the use of large volumes of data, including characteristics of local and global fields and information on processes in the photosphere, chromosphere, corona, and even heliospheric and geomagnetic disturbances, covering a long time interval. This is one of the reasons why the notion of the complex of activity has lately fallen into disuse. At present, the authors often prefer to consider instead the “complexes of active regions” (or even the “complexes of sunspot groups”). These do not require the use of extensive databases and, most importantly, are not supposed to live long. Many authors (e.g., see [7–11]) consider the complex of active regions as two or more ARs connected by a common magnetic field, whose components or parts interact in the course of evolution. The analysis of global complexes of activity is additionally complicated by the need to take into account the interactions of fields differing in their both spatial scales and intensity. Large-scale fields are, obviously, connected with the global magnetic field [12], and their evolution is controlled by processes deep under the photosphere, probably, at the bottom of the convection zone. On the other hand, the structure of a complex must depend strongly on the evolution of intense fields of AR, which are shallow features (5–10 Mm deep). As a rule, large-scale fields are associated with open field regions (OFRs), that is, the field whose force lines extend into interplanetary space and are carried away by the solar wind. These are the regions where CHs arise. Wang et al. [13] identified CH with OFR. Ever since, these terms have been used interchangeably to refer to CH observed in UV and X-rays on the disk and at the limb. Of course, this is a purely statistical coincidence. The open field regions are calculated in a complex way within the concept of the source-surface potential field with a lot of additional assumptions. The occurrence of CH depends not only on the magnetic structure, but also on the relative contribution of various heating mechanisms, which may somewhat differ in different CH. If the relationship between OFR and CH is quite understandable and the equal use of both terms is physically justified, another analogy that is frequently drawn is not as evident. Some authors identify large quasi-unipolar regions (UR) with open field regions and define CH boundaries simply as the boundaries of UR. Such an approach is physically groundless. Large quasi-unipolar regions may be the remnants of AR. Then, their field is shallow, and the field lines close inside the same region. Such regions do not form OFR, and their unipolarity index differs much from unity [6]. In the course of evolution, the OFR, CH, and AR form a single complex. Its properties are as follows. Magnetic fields in the chromosphere and corona that depart from the radial direction by less than 20° are the sites of occurrence of CH [14]. Despite the physical identity of these objects, their boundaries may not fully coincide and CH may occur somewhat later than OFR. 
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