Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

Positions ofX-ray emission sources o f solarflare obtained by MHD simulation should demand too large time for calculation. Such fast magnetic field change on the photosphere can cause disturbances with large current. However, the places of current sheets creation in any case must be X-type singular lines. Comparing of calculated position of the current sheet with the measurements of thermal X-ray emission The time interval r=6.108 s is taken as the unit o f time. For simulation in a reduced time scale the field evolution on the photosphere during the time т corresponds to real evolution during a day. The simulation is initiated from field configuration measured two days before the flare May 27, 2003 at 02:53. The moment 2.2 corresponds to the moment o f flare May 27, 2003 at 02:53 in the active region NOAA 10365. So this moment is chosen as for comparison with X-ray observations. The Fig. 1 presents lines o f the equal current density and positions of its maximums in planes, which are perpendicular to axis of the computational domain, in the moment t=2.2. X-axis and Z-axis are situated on the photosphere, X-axis is directed from East to West, Y-axis directed from North to South. The photospheric boundary of the computational domain is a square with the side of 400 000 km, which is ~ 4 times bigger than the size of active region. The active region situates in the central part of this square. The length of the square side is taken as the unit o f length. Y-axis is directed perpendicular to the photosphere from the Sun. The size of computational domain along the Y-axis is 120 000 km (0.3 in dimensionless units). The coordinate origin is in the Northern Eastern comer of the computational domain, which is rectangular parallelepiped of the form (0< jc < 1, 0<><0.3, 0<z<l). Fig. 1 presents the part o f computational domain with linear size of photospheric boundary 160 000 km (0.4 dimensionless units) of form (0.3<x<0.7; 0<y<0.3, 0.3<z<0.7) where the main magnetic field is situated. Fig. 2 Distributions of X-ray emission for the flare May 27, 2003 at 02:53 in soft and hard ranges obtained on RHESSI spacecraft (http://rhessidatacenter.ssl.berkeley.edu) . As the active region is situates near the solar disk center (S6 W5), the images in the picture plane (in perpendicular to line-of-sight plane) presented in Fig. 2, approximates well the projection on the plane y=const. Fig. 2 presents images of X-ray intensity for the flare May 27, 2003 at 02:53 in soft (1-30 KeV) and in hard (>30 KeV) ranges obtained on RHESSI spacecraft (http://rhessidatacenter.ssl.berkeley.edu) . Fig. 2 shows that the source of soft X-ray situated in the area 0.3389 <x< 0.5456,0.355 <z< 0.505, the boundary of this subdomain is marked by dashed lines in the projection y=const in Fig. 1. As the observations o f soft X-ray on the limb shows that the flare takes place on heights from 15 000 km to 30 000 km (from 0.0375 to 0.075 in dimensionless units) we can be practically sure that the position o f our flare is inside the interval of heights from 0.02362 to 01919 in dimensionless units. So one can see that the current density maximums are situated in the subdomain (0.3389 <x< 0.5456, 0.02362 <y< 0.1919, 0.355 <z< 0.505), their positions are marked on Fig. 1 in all three projections. The boundaries of this subdomain are also marked in Fig. 1 in all three projections. The local current density maximum in the considered subdomain on the height ~ 16 000 km is assigned in all three projections in Fig. 1 as Max ji. In the vicinity of this local maximum in the plane, which is perpendicular to magnetic field vector, the magnetic field configuration corresponds to the pronounced current sheet distinctly (see Fig. 3a). Taking into account that on such small height the magnetic field is large, the position of such current sheet must correspond to the solar flare place. Therefore, for clarity, the planes in all three projections in Fig. 1 are drawn through the point of this local maximum (0.46, 0.04, 0.445). Also in Fig. 1 in the considered subdomain in all three projections the group o f current density local maxima located is seen at the altitude o f 30 000 - 40 000 km (see projections z=const and x=const). For points of this group field configuration in the plane, which is perpendicular to magnetic field vector, is similar to the configuration of the point of this group marked in Fig. 1 as Max j 2. This field configuration is a stretched spiral (see Fig. 3b). It can occur due to strong disturbance appeared because o f the shortened time scale. Also, stretch of the spiral may be caused by focusing o f disturbances, which are typical for the current sheet, because in the projection x=const (see Fig. 3c) near this point we see the configuration o f the current sheet created in the vicinity of singular X-type point. 119