Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

N.M. Rudneva el al. Solar sources of very intensive and extreme storms Analysis of observational data for the period from 1 to 5 days prior to the storm, showed that extremely intense storms, in selected period, were observed after "halo"-type CME (and only in one case - alter "partial halo") accompanied by solar flares. The amount of storms corresponding to the certain selected characteristics of solar activity are shown at the Table I . As can be seen from the Table 1, very intensive storms were caused by "halo"-type CME, 13 of which occurred near the central meridian and only 3 - in the western hemisphere of the Sun. Ail of CME had a velocity in the corona > 700 km/s. Three of CME were accompanied by weak flares (Class C), and 13 - by strong (class X and M). Table 1. The distribution ot very intensive and Solar sources of intensive magnetic storms (-200 nT < extreme storms on the parameters of the solar [)s{ < . jqq „ j ) Analysis of solar sources was carried out for 66 intensive storms. The number of storms caused by type "halo"-type CME is 49 (8 o f them are "partial halo"-type). The number of storms caused by coronal holes is 9. Sources of the remaining 8 storms are defined less precisely, and. presumably, they were caused by active and disappearing filaments unaccompanied by CME. So intensive storms are caused most by CME associated with the flare or DSF. CME were accompanied by flares of high class, in some cases - by weak flares of class C. Often, before a magnetic storm it was observed not one CME, but several, one after another. In a series, CME could be accompanied by a number o f flares of different classes and DSF. It could be that a significant reduction of Dst-index is related with not the most energetic ejection. About a quarter of flares were long living. Coordinates of flares mostly close to the central meridian, but. in some cases, they removed to the western limb (more) or to the eastern one (less). In 6 of cases, CME were caused by sudden DSF in the absence of flares. The most frequently observed rate of CME was ~ (600 -700) km/s, but there were also low (~ 300 km/s c) and very high (> 2000 km/s) values of V. It should be noted: solar flares not only o f high class, but also weak flares can cause CME related to great geomagnetic storm; long living flares play significant role in the development of geomagnetic disturbances; in the period under consideration, phenomenons o f filament's disappearance, unaccompanied by flares, rarely (<10% ) led to a strong geomagnetic disturbances; coronal holes caused of intensive magnetic storms rarely. Location of solar power intensive and very intensive magnetic storms on solar large-scale magnetic field maps Flares and DSF. previous of CME. and follow magnetic storms occurred mostly near the HCS. on the boundaries of the OR-regions or the boundaries between the HCS and OR, if OR and the HCS slightly (20-25 degrees) away from each other. Storms number corresponding to possible localizations are shown in the Table 2. The Table 2 shows that the flares and DSF, previous to intensive and extreme magnetic storms, occur on the boundaries of sub-sectors (OR-regions) or near the HCS. This result confirms the conclutions of [Ivanov and Kharshiladze, 2002), and is an additional argument in favor of the view that activity complex are localized near sector and sub-sector boundaries. On coronal holes as sources o f geomagnetic perturbations It has been noted that the source of a geomagnetic storm is not some separate manifestation of activity on the Sun [Joselin and McIntosh, 1981]. it is known that the "pure" solar wind flows from coronal holes do not exist, and, as a rule, they are distorted by interaction with adjacent streams from another coronal hole or from filaments or flares. Our analysis of streamers from coronal holes confirmed this conclusion. In the Fig 1 (at right) the parameters of solar wind near the Earth's orbit are shown for the stream that flowed from the filament's area and coronal hole in July, 2003. OR-region and location of filament are shown at the top of the Fig.I. The filament disappeared by portions, while CME was not noted. Reduction of Bz IMF that leaded to Dst -110 nT was, most likely, related with a cold, dense and low-velocity flow from the filament than with a high-speed stream of coronal hole. The tendency of activity complexes located on boundaries of OR-regions (often coinciding with coronal holes), which was discussed above, explains the absence of "pure" solar wind streams from coronal holes. Table 2. Distribution storms relatively solar regions_______ _______ __________ Location Extreme storms Intensive storms Total number HCS 6 6 12 OR 6 42 48 HCS-OR 4 10 14 Total number 16 58 74 activity Solar sourse Number of storms X-class flare 7 M-class flare 6 С-class flare 3 HelioLongitude E < 1 8 °W < 4 0 ° 13 HelioLongitude W >40 ° 3 HelioLatitude < 22 ° 16 "halo" availability 16 "halo" velocity 700 км/с <V< 1000 km/s 4 "halo" velocity > 1000 km/s 7 "halo" velocity > 2000 km/s 3 21