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.

However, in this area we can see a few rhombs (high-shear magnetopause crossings) that correspond to the magnetic barrier presence for these events. As we can see in Fig. 2 such events are observed rarely. The large group of rhombs is below the shaded area. These rhombs correspond to events without signs of a magnetic barrier. However, there are 5 high-shear events in the shaded area. This is because the magnetic barrier accumulation time (-10 min) several times longer its destruction (1-2 min) [4]. Thus, in the presence of the dayside reconnection the probability of observing the magnetic barrier is determined by the ratio of the two characteristic times that is about 10-20%. Then we repeated the superposed epoch analysis for high-shear magnetopause events with signs of a magnetic barrier and without them. The results are shown in Fig. 3. The study o f magnetic barrier parameters dependence on the direction and intensity o f the interplanetary magneticfield Fig. 3 Superposed epoch analysis for 4 high-shear magnetopauses with signs of a magnetic barrier (left column) and 45 high-shear magnetopauses without them (right column). The format is the same as in Fig. 1. The magnetic pressure for the first subgroup increases while distance to the magnetopause decreases, there is also a layer with depleted plasma, low plasma p and increase of the plasma velocity in front of the magnetopause. The second subgroup is characterized by weaker magnetic pressure inside the transition layer and depleted plasma. These features indicate the absence of a magnetic barrier in front of the magnetopause. From the above it follows that the superposed epoch analysis does not give a correct answer to the question of whether exist or not the magnetic barrier in a case of southern IMF but gives an overall picture. We can see that presence of high-shear magnetopause events with a magnetic barrier does not affect the picture obtained by the superposed epoch analysis. After all we determined the reconnection rates at the magnetopause for each case with a destroyed magnetic barrier. The method from [5] was used to estimate the reconnection rates. For each event we determined the angle X. It is the angle between magnetopause reconnection line and axis Z at subsolar area. With that angle we calculated theoretical field magnitude В and density n in a magnetic barrier for different magnetopause reconnection rates g (0,1; 0,2; 0,3) by this formulas: f {Bm- B s cos в ) N A = arcsin к + В; - 2 B B . cos m s 0 } 1/2 £ = gMA2 s in (0 - A), В = (4 т т ^ У Щ ) , n = n0n ( £ ). 61