ИСТИНА

More than 5000 passes of DMSP F7 spacecraft through the auroral zone in the 21:00-24:00 MLT sector of both hemispheres were used for examination of the ion pressure (Pion) at auroral precipitation boundaries. Pressure values averaged for 5 seconds spacecraft observations of precipitating ions at poleward (Bpol) and equatorward (Beq) boundaries of auroral oval precipitation (AOP) zone and their association with solar wind dynamic pressure were analyzed. It was discovered that during magnetic calm (AL>-200 nT) as well as during magnetic disturbances ion pressure at the AOP boundaries increase with increasing of solar wind dynamic pressure (Psw). In the average during magnetic calm the ion pressure at Beq and Bpol boundaries increased from 0.3 to 1.3 nPa and from 0.1 to 0.3 nPa, correspondingly, when Psw changed from 1.0 to 7.0 nPa. Under the same Psw changes the Beq boundary shifted equatorward from about 68.0° CGL to 64.5° CGL. The result testifies the increasing of the pressure gradient in the inner magnetosphere under increased Psw and the geomagnetic field becomes more dipole like. Ion pressure changes at auroral boundaries during all phases of synthetic isolated substorm with the intensity about of -380 nT are shown. The average latitudinal profile of ion pressure in the region ±1° of Beq at the time of substorm onset is defined. At the onset time the average ion pressure at Beq was 0.85±0.15 nPa and latitude of Beq was 65.2°±0.6° CGL.