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.

N.A. Barkhatov et al. Besides the magnetic clouds orientation determined by magnetic field lines sunspot groups with the most advantageous location - leading and tail spots. It also has an impact on the number of magnetic storms that occur in different seasons of the year. In work proposes a seasonal variation model of geomagnetic activity that takes into account magnetic cloud orientation by the ecliptic plane. Under the proposed and tested hypothesis, the magnetic cloud orientation in space should be reflected in their geoeffectiveness due to changes in the values projection of axis magnetic field of clouds in the Earth's dipole during the year. 2. Annual evolution of axial projection of cloud magnetic field on Earth's magnetic dipole The presence of magnetic clouds orientation in space allows us to study effect of different configurations of these structures on geomagnetic activity. This is possible within the framework of calculating the projection of cloud axis magnetic field (B0) by geomagnetic dipole vector (M) as function of their relative orientation. Model calculation projections cloud axial magnetic field to Earth’s magnetic dipole performed on the assumption that it coincides with rotation axis. Calculation o f projections in spherical coordinate system carried out. In this case, orientation of vectors B0 and M, predetermined polarity (90° - e and 0) and azimuth angles (P and cp), respectively. During the year, vector M changes only angle (p, and angle 0 is 0 = 23° constant. As a result, expression for vector B0 projection on vector M is as follows: (B -M ) . I , . |B0| -( b xm x + b ym y + b zm ^ ( в хм х + в ум г + в 2м г ) B „M = 1 1 - = B „ COs(B0M ) = - -----------------;---- 7— j--------------= ------------- — --------------i L |M| |в 0||м | Iм ! where components of cloud axial magnetic field and geomagnetic dipole define as: Bx = B0 sin (90° - e) cos P, By = Ba sin(90° - s)sinp, B2=B0 cos(90° - e) > M x =A /sin0 co s(p , M Y =M sin 0 sin (p , M z - M cos0 Fig. 2 shows the change in year average monthly values of unit vector projection o f cloud axis magnetic field on geomagnetic dipole orientations for following events: e = 0°, p = 90° dashed line; s = 0°, P = 60° dotted line; e = 0°, P = 30° solid line; e = 0°, P = 0° dot-dashed line. 0.5 0,4 0,3 0,2 0,1 - 0,1 - 0,2 -0,3 -0,4 -0,5 1 2 3 4 5 6 7 8 9 10 11 12 months According to Fig. 2 during the equinox (months 3 and 9, dashed line) maximum projection give of magnetic clouds with small values inclination angle of cloud axis to the ecliptic plane £ = 0° P = 90°. In solstice times projection o f magnetic field o f such clouds on the dipole is zero. Because these clouds most often recorded in Earth’s vicinity [Bothmer and Schwenn, 1998], then the geomagnetic activity during the equinox should be increased. During the summer solstice, the largest contribution to geomagnetic activity should provide a cloud with s = 0° p = 0° (Fig. 2, dashed-dotted line). In equinox periods of projection of cloud axis magnetic field on geomagnetic dipole for such clouds is equal to zero. As the statistics observations o f magnetic clouds in Earth’s vicinity, such events are very rare [Bothmer and Schwenn, 1998] and a significant increase in geomagnetic activity they do not give. A similar analysis for different orientation of magnetic clouds was performed. He showed that by increasing the angle o f inclination o f cloud axis to ecliptic plane projection of the dynamics is preserved and its value increases. For clouds with an angle e = 90° for year value of projection remains constant for all values of P: such clouds are equally geoeffective regardless of the season. ^ 'У 'у / ' ' / \ \ 4 ' / / \ \ \ \ \ \ \ \ ' / / 4 \ \ ‘ \ \ \ \ / \ ' ' \ X' Fig. 2 Change during year average monthly values of unit vector projection of cloud axial magnetic field on geomagnetic dipole. The dashed line corresponds to the angle £ = 0°, p = 90°, the dotted line - e = 0°, p = 60°, solid line - £ = 0°, P = 30°, dash-dot line - £ = 0°, p = 0° 111