ИСТИНА

Ion pressure in different dayside precipitation regions was studied for dependence on IMF Bz component and solar wind dynamic pressure (Psw). For the aim of our investigation DMSP F6 and F7 spacecraft observations during periods of magnetic quietness (AL>-200 nT) for whole 1986 were used. The average ion pressure in the plasma mantle was found to be Pmant=0.02±0.01 nPa, which doesn’t depend on neither IMF Bz nor Psw. It was discovered that cusp pressure Pcusp was near to 1.0 nPa and it in common with Pmant doesn’t depend on Bz and under northward IMF on Psw. However, under southward IMF the pronounced enhancement of Pcusp with the increasing in Psw was observed from about 0.6 nPa during Psw=1.5 nPa up to about 1.7 nPa during Psw=6.0 nPa. The ion pressure in the region identified as the LLBL likewise to more high latitude regions mantle and cusp doesn’t depend on interplanetary Bz, while Psw substantially affected the LLBL pressure. In the noon hours (11:00-13:00 MLT) the PLLBL pressure changed from about 0.2 to 0.6 nPa along with Psw increasing from 1.0 to 6.0 nPa. The longitudinal profile of PLLBL shows the local hump of pressure near magnetic noon. This striking effect becomes most pronounced under high level of solar wind dynamic pressure: when Psw=6.0 nPa the average LLBL pressure was about 0.6 nPa near 12:00 MLT whereas only 0.3 nPa in the neighbor 10:00-11:00 MLT and 13:00-14:00 MLT. The average ion pressure in the region of structured auroral oval precipitation (AOP) was estimated to be 0.2 nPa and changed from about 0.08 nPa to 0.25 nPa with Psw increasing from 1.0 to 6.0 nPa. The level of PAOP slightly increased from noon toward both 08:00 MLT and 16:00 MLT under high solar wind dynamic pressure. The isobar of PAOP=0.2 nPa is closed in the ionosphere through the poleward part of nighttime AOP.